Apple-pie bed

This describes a practical joke where a bed is made up with a folded sheet so that the would-be occupant can only get his or her legs halfway down the bed. It has been a well-known prank both in boarding school and in the army since the 18th century. This has prompted the theory that its origin is a jocular military corruption of the French nappe pliée meaning folded sheet but this has not been substantiated. See Apple-pie order.