Specifically the door to my apartment. The very heavy, metal, self-slamming door to my apartment.
No matter what shenanigans the kids are getting up to in the hall, no matter how badly you need to use your right hand, which was holding the door, to break up whatever the hell they are doing that is making one of them screech that much, do not, under any circumstances, move said right hand until you are good and sure that your left hand hasn’t found its way into the crevice between the door and its frame, over by the hinges. Especially if you are the only parent at home.
On the plus side, checked out the new local ER, where everyone is very nice, and found out which neighbor will come to check if you really, really, really scream. And I got some classy pics of my somehow not broken fingers.