You ask for parietals if you want to have a MOS in your room. Parietals is not the act of banning them from your room, it is the practice of asking permission, and, at some places, leaving the door partly open (with a shoe or something.) It does not START at midnight.
female boarder: hey, you want to come up to my room????
random guy: um, ok, but shouldn't we ask for parietals or something? Don't want to get in trouble.
"It's not the groping that goes on behind closed doors that I worry about-- it's what goes on behind the open doors that bothers me!"