I own a Qi car charger with a little button on the back surface that, when pressed (when you press a phone's back against it), causes arms on each side to release and clamp down on the phone.
This worked great until I bought a Peak Design phone case which has a hole in the back of it for their attachment system. When I press the phone against the car charger, the button never gets pressed, so the arms never clamp to the phone, and I end up doing this awkward slip-my-finger-behind-it button pressing dance to get the phone to lock in place.
Since I don't use their attachment system for anything (I only bought the case because of the integrated magsafe-style magnet and the nice cloth back), I made this little plug to solve the problem. Just place the square into the indentation (with the raised side facing toward you), and turn it 45° (maybe with a pair of tweezers, if you happen to have giant fingers like mine) until it “clicks” into place. It will be a relatively tight fit, but should also be removable in the same manner.
I printed it in PETG, but just about anything should work. (TPU might actually be an interesting choice, for the texture.)
The author marked this model as their own original creation.