Red one piece union suit has funny Rear flap with a DANGER – BLASTING AREA – KEEP CLEAR sign screen printed on the flap. These non-footed one pieces can be worn as pajamas or loungewear. Men or women can also wear these as one piece long john underwear or thermal underwear. Lighter than the original wool union suits, these jersey cotton one pieces are more like your favorite t-shirt, but (no pun) they still have the convenient drop seat, also historically referred to as butt-flap, bum-flap, access hatch, fireman’s flap and trap door.