(current version of the designer: 61 – updated Feb. 6, 2024)

Keyguards give individuals with limited muscle control the ability to point reliably at regions of an app running on a tablet. They do this by physically separating access to specific regions of the tablet screen with rails that rise up from the surface of the tablet. In this case, the apps are associated with Augmentative and Alternative Communication (AAC), however, any tablet app can be supported by designing a free-form keyguard.

Ways to obtain a keyguard

There are two ways to obtain a keyguard design:

You can choose among the pre-designed and ready-to-print keyguards that we’ve created for the most popular AAC apps on the most popular iPads. If that sounds promising, then go here for 3D-printable designs, or go here for laser-cuttable designs.

You can design your own keyguard. This may be necessary if you use an app/tablet/case for which we haven’t created a pre-designed keyguard or if you want to learn more about what’s possible. If that sounds right, read on.

Designing a keyguard

What’s involved in creating a 3D printed keyguard?

Watch this video to see how easy it is to design your own custom keyguard:

The video takes advantage of concepts described on these four web pages:

Watch this video to see how your design gets turned into a physical keyguard:

For a sense of the range of keyguards you can produce with this designer, watch the following video:

But how do you print your keyguard design if you don’t have a 3D printer? Watch the video below:

If you have more time, the following video is of a 3.5 hour workshop, entitled “3D-Printed Keyguards – from Soup to Nuts”, that I lead as part of the Assistive Technology Conference of New England 2021-2022. The slide deck is available for download here. Note that the designer has undergone several changes since this workshop was recorded. Fortunately, the core concepts haven’t changed.

—–Is it possible to get a complete AAC system for $96? Yes it is.

The Whole Story

Many AAC apps organize their content into a grid of rows and columns with menus and message bars, above or below the grid.

Others are much more creative and unpredictable in their layouts.

Hybrid apps are largely grid-based but their keyguards can be enhanced by selectively exposing specific regions of the app, adding engraved text, or cutting out parts of the edge of the keyguard so it can fit in an oddly shaped case.

The number of possible choices for tablet, tablet case, and AAC app, make it impossible to design a few keyguards that will meet everyone’s needs. To complicate matters further, users have lots of flexibility in how they organize the content in their apps. All of this is to say that users need to be given control over the keyguard design. We know of only one 3D modeling tool where that’s possible – without requiring each user become an expert in 3D modeling. That tool is OpenSCAD. OpenSCAD has a “Customizer” feature that allows designers to provide input to an OpenSCAD design that can shape the design to meet their specific needs.

We have created an OpenSCAD designer that allows people to identify their tablet, describe how the AAC app is laid out, describe their case, and choose a mounting method to mount the keyguard directly to the tablet or to the case. Once the keyguard is fully described you can generate and save an STL file that you can print on your 3D printer.

Commercial keyguards are often made from a sheet of acrylic using a laser cutter. Many of these keyguards are constructed for a specific app and represent a generic layout for that app. Because they’re made from a flat sheet of plastic they can only be mounted in a limited number of ways. These keyguards normally cost anywhere from $40 to over $100. A 3D printed keyguard can be as customized as you need, is not limited to being flat so it can be mounted in a variety of ways, can be printed in a vast number of colors, and best of all, costs $0.75 to $1 to print. At that cost, you can easily have multiple keyguards for multiple app configurations and multiple apps.

First Things, First

Before you begin, you’ll need to go to Printables.com to get a copy of the keyguard designer.

Download the two files from the Printables “Files” tab: the “keyguard.scad” file and the “openings_and_additions.txt” file. Put them both in the same folder.

You will see a “v” followed by a number as part of the designer’s file name – that’s just the version number. It will change over time so we won’t include that specific information in these instructions.

Follow these instructions to download OpenSCAD and open the keyguard.scad file. You’ll also need a good text editor like the free program Notepad++ to edit the openings_and_additions.txt file. Follow these instructions to download Notepad++. You can also use Windows Notepad. Just don’t use a more sophisticated program like Microsoft Word. You can easily insert characters into the file that won’t make sense to OpenSCAD.

Note that you can use the built-in program, Notepad, on Windows, instead. If you have an Apple Mac you can use the built-in text editor called TextEdit. Be sure that the format is set to “Make Plain Text” so that no special/hidden characters are inserted into the files.

Keep a Record

It’s smart to record your decisions about the keyguard that you want to design and print. We provide a form for collecting this information. The data form is available as a DOCX or PDF. The form is laid out exactly like the instructions below and will be especially valuable if you ever want to modify or replicate a keyguard design later. The form is described in detail here.

As you make decisions and take the measurements of your tablet and case, record those decisions/measurements in the data form as a record and to make entering them into the designer easier. Also, take a screenshot of the application running on the target tablet and keep that screenshot with the data form. Finally, take a picture of the app running on the tablet in the case. This complete picture can help when determining how the tablet fits in the case and whether the mounting method you’ve chosen could be a problem.

The Customizer Pane

The Customizer pane of OpenSCAD is organized into categories.

You’ll want to go through the customizations from top to bottom. Here are all the customization categories available:

The Type of Keyguard section contains a single option where you decide whether you plan to design a 3D-printed keyguard or a Laser-cut keyguard. You choice will determine which options you can control and which ones you can’t. It’s also the place to set the basic thickness of your keyguard.
The Tablet section contains options for the kind of tablet you want to use, whether you use it in landscape or portrait mode, and whether you want to show or hide the Home button and front-facing camera.
The Tablet Case section contains options for describing the amount of the tablet’s face that’s exposed once it’s in the case.
The App Layout in px, App Layout in mm, and Bar Info sections contain options for describing how the regions of the app are laid out on the screen. You will use either the App Layout in px or App Layout in mm categories, not both.
The Grid Layout section contains options for describing how the grid of buttons is laid out and how you would like the rails that separate the grid of buttons to look.
The Grid Special Options section contains additional options for fine-tuning your grid layout. You will use these options less frequently but they will be very helpful when you do.
The Mounting Method section is where you specify how you would like to mount the keyguard or keyguard frame to your tablet or case.

The next four sections: Velcro Info, Clip-on Straps Info, Posts Info, Shelf Info, Slide-in Tabs Info, Raised Tabs Info, and Keyguard Frame Info depend on the mounting method you’ve chosen.

The Braille Inserts section contains options for creating a rectangular piece of plastic that can be squeezed into any keyguard opening. The piece contains one or two sections of Braille text and a hole for accessing the surface of the tablet.
The Free-form Keyguard Openings section contains information that the designer needs to know in order to correctly interpret the instructions you put in openings_and_additions.txt.
The Special Actions and Settings section contains options that help you to fine-tune and tweak your design.

Next, we’ll describe each section. Remember, the best way to go through these options is from top to bottom.

Before we move on… If you want to preserve the changes you make to the settings in the Customizer, do that by creating a Preset for your design. DON’T DO A FILE>SAVE! That will just create a copy of the keyguard designer program – which is totally unnecessary and will make your life harder!

What Kind of Keyguard are you trying to Design?

You have more control over the design of your keyguard and more features available to you if you 3D-print your keyguard, so why would you pay more for a laser-cut keyguard? There are three reasons:

If you want your keyguard to be perfectly clear, then you need a laser-cut keyguard. Even if you use clear filament, a 3D-printer cannot turn that into a clear object. You can read more about “why”, here.
If you need a very strong keyguard, a laser-cut keyguard will probably be stronger than a 3D-printed keyguard. That’s because a laser-cut keyguard is made from a solid sheet of acrylic rather than thin layers of plastic – each of which is created from thin threads of filament.
If you need a really big keyguard, and you want that keyguard to be a single piece (rather than two pieces that have been joined together), then you can make a keyguard that is arbitrarily large in size on a laser-cutter.

Our keyguard designer is typically used to design a 3D-printable keyguard but it’s also possible to take your design, and with a few restrictions, use the design to create a laser-cut keyguard.

We worked with the folks at Keyguard AT to come up with guidelines that will make your keyguard durable and reliable when it’s laser-cut. You can send your design to Keyguard AT for them to laser-cut or, if you have access to a laser-cutter, make it yourself.

A laser-cut keyguard will always be more expensive than a 3D-printed keyguard so we recommend that you first 3D-print your keyguard design and, once the design is exactly right, send your design off for laser-cutting. Read more about the process of creating a design that’s ready to be laser-cut, here.

By default, several restrictions are placed on your laser-cut keyguard design. These restrictions are intended to ensure that your keyguard will be strong and resilient. If you believe that these restrictions are too constraining, you can lift the restrictions by setting the value of “use Laser Cutting best practices” to “no”:

Finally, set the thickness of your keyguard. You’ll see later that the grid rail height can’t exceed this value. Also note that this value will not exceed the thickness of your keyguard frame if, by chance, you’re inserting your keyguard into a frame.

Describing your Tablet

The Tablet category of customizations looks like this:

Click on the pull-down list under “type of tablet” and select your tablet:

The designer supports all currently available iPads and many other tablets. The program can be extended to support additional tablets. You’ll first need to obtain certain key measurements. You can learn more about extending the designer here.

We include support for several NovaChat, Accent, and GridPad systems. You can learn more about designing a keyguard for these systems here.

If you’re unsure what type of tablet you have, follow these instructions:

Next, choose how you will be using the tablet – in landscape mode or portrait mode. This may depend on the tablet case you’re using. Many cases have stands that only support using the tablet in landscape mode. Most AAC apps are designed to be used in landscape mode. They may also support portrait mode.

At the end of the pull-down list you’ll see a special entry called “blank”. This entry is intended for use when you create free-form keyguards of arbitrary size. This is the option you would choose if you wanted to create a keyguard for a standard PC keyboard. More on that process can be found here.

You need to specify whether you want to expose the Home button and front-facing camera. If the keyboard will be used by an individual who would be distracted by these openings in the keyguard, you may want to keep them covered. Note that certain mounting options for the keyguard make the keyguard harder to remove than others. That may mean that you will need to keep the Home button accessible. Also note that some cases provide easy access to the Home button. The keyguard can’t cover up the Home button or camera if the case already makes them accessible.

You can make the home button more or less accessible by varying the slope of the sides of the opening:


30 degree slope (default)	90 degree slope

The default orientation of the keyguard in in landscape mode and has the home button on the right and the camera on the left. Some cases with built-in handles require that the camera and home button positions be swapped:

If the tablet will be used in this case orientation, just set the “swap camera and home button” option to “yes”.

As an alternative, you can instruct the designer to create symmetrical cuts in the keyguard that accommodate both the camera and home button:

With this design, the case can be rotated and then the keyguard can be rotated without making the camera, home button, or ambient light sensors inaccessible.

Finally, you may find that the openings that are automatically put in your keyguard design to expose the ambient light sensors in your keyguard. Unfortunately, they can make your keyguard weak if the boarder is already thin as a result of a very tight case opening. To get rid of these openings, set “expose ambient light sensors” to “no”. That may cause your screen to dim even when the tablet is in a very bright setting. You can tell your tablet to ignore these sensors in your tablet’s settings.

Describing your Tablet Case:

If you don’t plan to use a case with the tablet, you can ignore this category of options – except to change the value of “have a case” to “no”. If you do, leave it set at “yes”.

You need to take three measurements of your case: height of opening, width of opening and opening corner radius.

It’s most accurate to take these measurements with the tablet in the case. All measurements are in millimeters and only whole numbers can be used. Don’t take your measurements where there are cut-outs for the camera or Home button.

When measuring the opening of a hard-sided case, even a soft case with an inner hard-plastic screen protector (see below), round down to the nearest millimeter value to ensure that the keyguard will fit close to the surface of the screen protector.

Measuring the opening in your case may be hard to do accurately with a ruler. For the most accurate measurements you may want to print an Easy Measurement Tool.

You can add extra plastic to the perimeter of the keyguard if the case opening is very close to the edge of the screen. Note that there’s no free lunch, adding plastic will make your keyguard more sturdy but it will also result in loosing access to active areas of your app.

Note that you can get a pretty good idea of the height and width of the opening in your case by going to the Keyguard AT website and checking whether your case matches one of the over 400 cases they’ve measured. You’ll still need to estimate the corner radius of the opening. Guessing a number that’s a little too large will work better than guessing a number that’s a little too small.

Describing your App’s Layout:

[This category will probably be irrelevant if you are designing a keyguard for a free-form app.]

keyguard.scad makes the assumption that all grid-based AAC apps have a basic layout that looks like this:

Each region can be a different height – including no height at all, if it’s not there. There’s nothing special about a message bar or a command bar – just that message bars tend to be above any command bar. Just think of them as two regions at the top of the app and two regions at the bottom that can take up part of the screen and may need to be exposed or hidden.

The TouchChat app, pictured below, has a status bar, an upper message bar, an upper command bar, and below them, a grid of buttons arranged in rows and columns. It has no lower message bar and no lower command bar.

The GoTalk Now app, pictured below, running on an iPad Mini, has a grid of buttons above a lower message bar and a lower command bar. It has no status bar, no upper message bar, and no upper command bar.

Note that the GoTalk Now app moves the message bar to the top of the screen for larger iPads.

You can measure the layout of the app in pixels or in millimeters:


measuring in pixels	measuring in millimeters

To measure the app in pixels, load a screenshot into a graphics editor like MS Paint. To measure the app in millimeters, you’ll just bring up the app on the target tablet and get out your metric ruler. We prefer to measure the app in pixels using a screenshot of the app. That’s because the screen has about 10x as many pixels as millimeters. Go here to learn more if you’d like to use screenshots to measure each of these regions.

Enter your measurements in to only one of these sections, not both – there’s no need. But there’s also no danger. If the designer sees that you’ve put values into the “App Layout in mm” section then it will just ignore anything you’ve put in the “App Layout in px” section.

If you’re measuring in millimeters and a bar doesn’t exist you just leave its height at 0 mm. If you’re measuring in pixels and a bar doesn’t exist just repeat the value you used for the previous measurement (for upper bars) and the next measurement (for lower bars). If there are no lower bars, put the total number of vertical pixels in these two boxes.

Exposing or Hiding Bars

Now that you’ve specified the vertical size of each bar in the app layout – including whether some of these bars even exist – you can now tell the designer to expose a bar or leave it hidden.

In addition, you can adjust the slope of one edge of each of the exposed bars. By reducing the slope from the default value of 90 degrees, you can provide greater manual and visual access to that bar. Note that the additional access has to come from the adjacent bar. If you’re exposing two bars that are next to each other, this option won’t have any effect on the keyguard. This page provides a detailed explanation of this option.

Finally, you can add rounded internal corners to your bars to improve the overall strength of the keyguard. If you select “no” the bar will have 90-degree internal corners. If you choose “yes”, the internal corners will be rounded:


rounded = yes	rounded = no

If you want to expose just certain regions of a message or command bar, you can choose to set the “expose…” option to “no” and then cut openings in that solid bar, for those items that you do want to expose, by providing the location and size of the openings in “openings_and_additions.txt”. Follow the instructions on this page to provide those instructions. This same approach can be taken if you want more control over the shape of a bar or the slopes of its sides.

Describing your Grid’s Layout:

The Grid Layout category is packed with options. This image is the first and most often used options of the category:

The first two options are straight forward. Match the number of columns of buttons in the app to the number of columns option and similarly for the number of rows of buttons in the app. If you’re designing a keyguard for a free-form app, set the number of columns or rows to zero and then follow these instructions to describe where the openings in the keyguard should appear.

The next four options are a little more complex and interrelated.

When a typical keyguard is laser cut from an acrylic sheet, all angles are cut at 90 degrees. This can produce sharp edges that are painful during use. keyguard.scad gives you more control over the rails between buttons. Each rail looks like this in cross-section:

You set how wide the rail should be, how steep or shallow the slope should be and your preference for how high the rail should get before it gets clipped off.

It’s called the “preferred” rail height because you always get the rail width and slope that you want – and, if possible, you also get your preferred height. As you can see from the image below, the preferred height can be set higher and higher (images 1 and 2) but there comes a point (image 3) where the height just won’t get any greater without increasing the width or increasing the slope:

Setting the preferred rail height higher than the height of the rail in image 3 won’t have any effect. You can see how high the rails are at any time by looking at the Console pane in bottom of the OpenSCAD window. The second (or so) line in the pane (you may have to scroll up to see it) will look like this:

In this case, the line says “ECHO: rail_height = 5”. That number is in millimeters. It also shows the maximum rail height for this slope and rail width. If you set the preferred rail height higher than the maximum, the number in the ECHO line won’t change You’ll have to increase the rail width or slope to get what you want. A rail slope of 90 degrees will allow you to make the rails as high as you’d like (“inf” stands for “infinite”) . While you “can” create rails as high as you’d like, you can’t exceed the keyguard thickness that you set in the “Type of Keyguard” section. So if your rails aren’t as high as you’d like, first increase the keyguard thickness. By decoupling the keyguard thickness from the rail height you can reduce the height of the rails, thereby giving the user easier access to the tablet without necessarily weakening the keyguard.

The keyguard, as a whole, and the rails are all at the same height (thickness). So a rail height of 5 mm, like the one above, will produce a keyguard that is 5 mm thick. Such a keyguard will be plenty strong but you should be wary of letting your keyguard get thinner than 3 mm. It may require special handling when not in contact with the tablet.

Cell openings begin as rounded-rectangles with 3 mm rounded corners. If you set the value of “cell corner radius” to 0 mm, the openings will become simple rectangles.

By default, grid openings use rounded rectangles with a 3 mm corner radius. You can create rectangular openings by reducing the radius to 0 mm. The designer will ignore the value if you set the corner radius to a value larger than 1/2 of the opening’s shortest side. If you would like circular openings you’ll work with both the rail width and corner radius settings to create them. More on that topic here.

Special Settings for your Grid’s Layout:

These options will let you take your grid layout to the next level and accommodate idiosyncrasies in certain AAC apps.

The slope of the top and bottom edges of a of the cell opening can be controlled independently by the “cell top edge slope” and “cell bottom edge slope” options. Much like controlling the message bar edge slope, you can use this option to provide better visual and manual access to small rectangular openings when the tablet is held at a low or high angle.

You can also choose to cover and/or merge certain cells. Cells are numbered from the lower left to the right and then up to the next row. A detailed description of these three options can be found here.

For individuals with vision impairments, you can single out certain cells by putting a raised ridge around them:

To select cells for ridges, enter the numbers of the cells (separated by commas) between the two square brackets. In this example, keyguard.scad will put raised walls around cells 1, 2, and 7:

This image shows 2 mm wide and 2 mm high ridges around rectangular cells:

The ridges can also be applied to circular openings and can be made taller and a little wider:

These ridges are even wider and have been applied to rounded rectangular openings:

If you make the ridges too wide they will extend into surrounding openings. Note that ridges work best when the grid openings have 90 degree slopes. They can be used with sloped openings but the will have to be narrower because the top edge of the opening will also be narrower.

You can use this feature, along with some lines in the case_additions and case_openings data structures to create the equivalent of a PRC Touchguard for it’s Lamp Words for Life – VI application:

PRC charges $165 for its touchguard. You can 3D-print one for $1.30.

The next four “padding” options are “fudge-factors” that you can use to make the keyguard fit your app even better. Go here to see if your app needs these fudge-factors.

Finally, when the case opening is the same size, or only slightly larger than the size of the screen, the final keyguard design will have a very thin and flimsy border. The next four options allow you to add a thicker boarder. You can learn more about these options on this page.

Describing the Mounting Method:

You will need some way to attach the keyguard to your tablet. You can’t just set it on the glass because it will be too slippery and will slide around. There are a couple of ways to attach the keyguard when you’re not using a case and a couple of ways when you are. The Mounting Method category is where you choose the mounting features that will be added to the keyguard. The “No Mount” option has a couple of special applications that will be described at the end of this section.

If you’re not using a case, the typical attachment methods are with suction cups, screw-on straps, clip-on straps, or Velcro:

If you are using a case, the typical attachment methods are slide-in tabs or raised tabs:

If you have a particularly inquisitive student or client who likes to remove the keyguard, clip-on straps may be the best solution:

You can use any of the three methods with a soft-sided case but only raised tabs and clip-on straps can reasonably be used with a hard case or a soft-sided case with a hard, screen protector insert.

The “No Mount” option doesn’t add any special features to the keyguard. Instead, it allows you to use special “suction-cup tape” (sometimes called “micro-suction tape”) to attach the keyguard directly to the tablet glass, or you can simply “wedge” the keyguard into the opening in a soft-sided case. If you have space on the keyguard, using the micro-suction tape is often the best option whether you have a case or not.

The “Posts” option applies only in those instances where the case manufacturer provides a special mount that can receive keyguards of this type.

The “Shelf” option is similar to putting a set of slide-in tabs all the way around the keyguard. When used along with a keyguard frame, you can create something very like the screen protector that comes with many cases. Mounting a keyguard (or keyguard frame) with a shelf makes it difficult to remove and insert the keyguard but that may be exactly what you’re looking for.

The table below may help in choosing the best mounting method for your needs. Follow the links for instructions regarding each mounting method.

Mounting Method	Used with a Case	Used without a Case	Easy to Swap Keyguards	Fits Close to Screen	Stable Mount
No Mount	x	x	x	x	x
Suction Cups		x	x		x
Velcro		x	x		x
Screw-on Straps		x
Clip-on Straps	x	x	x	x	x
Posts	(x)		(x)	(x)	(x)
Shelf	x			x	x
Slide-in Tabs	x			x	x
Raised Tabs	x		x	x	x
* Keyguard Frame	x		x	x	x

(x) Posts are only applicable if the case is already fitted with a post mounting frame by the manufacturer. If the space between the case opening and the screen is large enough (approximately 10 mm) then you can use a keyguard frame to get the same effect. See the “Posts” description at the bottom of the Keyguard Frame webpage.

The “No Mount” method is really two different approaches. Each approach has it’s pluses and minuses. Follow the link above to learn more.

* You won’t see “Keyguard Frame” in the Mounting Method pull-down list. It’s a specialized keyguard design where you 3D-print a frame that surrounds your keyguard. A keyguard frame can make it easy for you to quickly swap keyguards or even design a “flip-up” keyguard. You can use this frame to make a screen protector and use it in place of the screen protector that came with your case. You then print your keyguard and frame separately, as a matched pair. Other keyguards can then be designed to fit within the same frame and swap between them as necessary. You can also use this method to add a screen protector and keyguard to a case that doesn’t come with one. You can choose between No Mount, Shelf, Slide-in Tabs, or Raised Tabs as the mounting method for your keyguard frame.

Depending on the mounting method you choose, you may need to provide additional information. There are seven categories of options that must be used to set those options: Velcro Info, Clip-on Straps Info, Posts Info, Shelf Info, Slide-in Tabs Info, Raised Tabs Info, and Keyguard Frame Info.

Adding Cell Inserts


simple cell insert	Braille cell inserts

There are a couple of reasons that you might want to cover an opening in the grid. You can create rectangular inserts that squeeze into each rectangular opening in the keyguard.

The simplest reason to cover a cell is that you just don’t want the tablet user to be able to touch one or more of the buttons in the grid region of the app. As you’ve read above, you can build a covered region directly into the keyguard, but what if you want to restrict access just for a short period of time? If that’s what you want, then you can create a solid insert that squeezes into your keyguard and can be removed when you’re ready. Using a contrasting color for your cell insert can serve to help the user target that location prior to exposing the app button underneath.

You can also use cell inserts to give Braille-capable individuals a voice by putting Braille on the insert that corresponds to the word in that cell and an opening in the insert for touching the face of the tablet. The insert has at least one area of Braille text and a round opening for interacting with the tablet. Unfortunately, the more elements you place on an insert, and the larger those elements, the larger the insert must be. That may require that you have a larger tablet and/or fewer cells per page.

The options in the “Cell Inserts” section support you in creating either type of insert.

To create a simple cell cover, leave the “Braille text” field empty and set “add circular opening” to “no”.

Braille inserts have much more flexibility. You can read more about the design of Braille inserts on this page.

To generate an STL file for one of these inserts, choose “cell insert” from the “generate” pull-down list in the “Special Actions and Settings” section.

The insert is intended to wedge tightly into place. If your printer typically over-extrudes or under-extrudes you may need to adjust the tightness of the fit (i.e., the size of the insert). The “tightness of fit” can be adjusted from -10 to 10. A value of -10 makes the insert 1 mm smaller in height and width while a value of 10 makes it 1 mm wider. Start by printing your keyguard and then print a sample insert. Adjust the fit as necessary.

The following video demonstrates how these inserts are squeezed into place in the keyguard. Though the insert used is a simple insert, the process is exactly the same for Braille inserts.

Remember that the inserts are rectangular so the openings in your keyguard must also be rectangular. For the best fit, set the “rail slope” of your keyguard to 90 degrees.

Finally, by default, inserts are as thick as the rest of the keyguard. If you would like to tactilely separate the the inserts from each other, you can create a recess between the top of the inserts and the rails between the cells by increasing the value of “insert recess”.

Because these inserts are small parts, ensure that the user cannot remove them from the keyguard and attempt to swallow them.

Describing your Free-form or Hybrid Keyguard Opening Data:

The Free-form and Hybrid Keyguard Openings category contains options that help the designer interpret the numbers you will provide in openings_and_additions.txt about where every opening should be located and the opening’s shape and size.

First, there’s an option to specify how thick your free-form keyguard should be. A thicker keyguard is more rigid and reduces the chance that the user will accidentally make contact with the tablet. A thinner keyguard makes it easier to physically and visually access regions of the screen. Remember to set the number of rows or the number of columns to zero if you’re creating a free-form keyguard.

If you’re designing a hybrid keyguard, the thickness of the keyguard will be determined by the height of the rails between the grid buttons.

The remaining options get specific about how you took your measurements. You can measure the location and sizes of the interactive objects of the AAC app (where openings in the keyguard will be placed) in units of pixels or millimeters. If you took your measurements from a screenshot, then units should be set to pixels. If you took your measurements directly from the app running on the tablet using a ruler, then units should be set to millimeters. You can take your measurements relative to the upper-left corner of the screen (or screenshot) or relative to the lower-left corner.

If you’re testing your measurements and strange things are happening – like no openings are appearing or they’re in the wrong place or wrong size – you may have one of the above options set incorrectly.

Collecting Measurements for a Free-form or Hybrid App

There are several steps necessary to properly collect and record the measurements for a free-form or hybrid app. It makes more sense to cover that information on a separate page: Specifying a keyguard for a free-form (or hybrid) AAC app

Tweaking your Design:

Normally, you will use the designer to “generate” and print a “keyguard” but there are also options to print one or two clips if using the clip-on straps mounting method, or a cover for one of the cells in your keyguard. You can also separate your keyguard into two pieces and print each one independently if your printer is a bit to small to print the whole keyguard in one piece. You then use an adhesive like super glue to glue the two halves together. You can also generate Braille inserts as described above. You can generate just the first layer of your design that can then be exported as an SVG or DXF file and laser-cut. Finally, if you’d like to share your Customizer settings with someone else, follow the instructions on this page.

Almost all cases are designed so that the display screen sits evenly between the left and right, and the top and bottom edges of the opening in the case. There are special cases (pun intended) where that’s not true. If you have one of those cases, you’ll need to shift the app/grid region of the keyguard. You can learn more about how to do this and the last two options on this page.

When splitting your keyguard in half so it will fit on your printer, you have the option to join it together with dovetails or to leave the interface flat. While the designer will attempt to split the keyguard along a rail near the middle of the keyguard, you can control exactly where the split will occur. This can come in handy when testing the fit of a keyguard design and you only want to print a small part of the keyguard.

You can make fine adjustments to the size of your keyguard with the “keyguard tightness of fit” sliders. This can be valuable if you’re wedging the keyguard into place inside a rigid object like a screen protector.

If you’re using an older computer or a computer with limited memory, it can have trouble creating or slicing a keyguard design with lots of circles or rounded corners. This can result in your design taking a long time to display or it may not display properly. If this happens to you, try setting the “smoothness of circles and arcs” to a lower number. The lower the number, the more jagged the edges of circles and rounded corners will appear – though the jaggedness may not be visible in the 3D printed keyguard – so feel free to experiment with different values.

The option “trim to screen” is useful when testing the layout of your keyguard and how well it matches the actual layout of the AAC app. More on that topic can be found here.

The option “cut out screen” is useful when measuring for a new tablet or new case. More on that topic can be found here.

If you have a screenshot of your app, you can display it “live” along with your keyguard design. More on that topic can be found here.

When testing the fit of your keyguard, it can be useful to print just the first 0.4 mm of your keyguard (i.e., the first two layers if printed at 0.2 mm per layer). More on that topic here.

Finally, you can print just a region of the keyguard by identifying the coordinates of the lower left corner and upper right corner of that region. This is especially useful when designing a very large keyguard.

Finally, you can design a keyguard for an “unsupported” tablet by selecting “other tablet” from the “type of tablet” pull-down, and then provide a small set of measurements for your tablet. Most of those measurements go between brackets in the “other tablet general sizes” box”. Three more measurements associated with the tablet’s screen pixels go in the “other tablet pixel sizes” box. More on that topic, here.

Do you have any ideas about how to improve this design? Provide some information below:

Customizable, 3D Printable Keyguard for Grid-based, Free-form, and Hybrid AAC Apps on Tablets