Punk Butt Flaps
A butt flap, also known as a bum flap is probably one of the funniest pieces of punk rock fashion. They are basically a piece of cloth, usually covered in a patch that hang on the butt of a punk's pants. The only real purpose I know of for butt flaps is to give an extra layer of comfort/warmth when sitting on a sidewalk (and likely begging for change).
But flaps are popular among street punks. They look something like this: