I swear, every theatre I've been in (even a couple without fly systems) use fly bricks to hold open doors. It's hilarious

For those not in the know, fly bricks are massive lead weights used to counterweight the fly system. They tend to get scattered all over the theatre, since they get moved around from flyline to boom pipes to random places so often.

it's always fun when you fetch a couple bricks from the loading gallery, set them down, then loose one only to find it hours later holding open a door. (yes, that's happened xD)