Simple hook/latch that I whipped up for my work to deter people from wandering where they shouldn't. Quite simple in design; put the hook on one side and tie some string, chains or anything similar to it. Attach a pin to the other end and simply slot it into the hole.

I just tied some string to the hook, cut and filed a nail as the latch and put a sign on the string.

Prints perfectly without supports.