My wife and I were given an antique chest with an old lock, but no key. I realized it needed a type of skeleton key, and what better way to create a custom out-of-date key than a 3D printer? I probed the lock with a small allen wrench and calipers to figure out where the notches needed to go. I printed a prototype key and was amazed that it worked on the first try. I tweaked the sizes a touch to make the fit smoother, made it pretty and printed the one you see here. Total time from measuring to trying the first key was about an hour.

I doubt this particular key will fit anyone else's lock, but I've included my OpenSCAD file, which you can modify to fit your desired key dimensions if you have a need. I'm quite impressed that PLA is plenty strong enough to open and close this lock (it has a stiff spring). And the best part is, if I ever do break it, I can print a replacement in about half an hour.