If you’ve tried sticking a Velcro dot (one or four depending on your design) into the recessed slot on the back of your Bliss Tactile Symbols and the don’t seem to stay attached to the symbol, this may be why.
When creating the slot, your 3D printer will stretch thin lines of filament across the opening to the slot. They look like this:
They’re thin enough that they might not provide enough surface area for the dot to stick to.
You can address this issue by using a hair drier to heat up the Velcro dot and its adhesive and then pressing the dot and the slightly melted adhesive in between and around the thin filaments.
The video below provides a demonstration: