I have small kids, sometimes doors get locked to empty rooms. The inspiration for this was when I was cleaning out my wallet yesterday and found an old gift card that I've carried for YEARS for opening doors. The card looked terrible, and it was starting to crack.. so I printed this credit-card sized bypass tool.

The small recess is sized to push the latch for a door that opens inward. The larger cutout is sized to slip over the latch for a door that opens outward.

I printed this in PETG and it's really flexible, I haven't tried in PLA yet. I can say that the PETG doesn't have any issues with bending pretty severely. I've got one in my wallet and it is the same size as a credit card.