A strike plate is a metal plate affixed to a doorjamb with a hole or holes for the bolt of the door. When the door is closed, the bolt extends into the hole in the strike plate and holds the door closed. The strike plate protects the jamb against friction from the bolt and increases security in the case of a jamb made of a softer material (such as wood) than the strike plate. A plate on the lockset itself (on the door, not the jamb) is instead called a face plate.
Some strike plates have their hole size and placement calculated so a spring-bolt extends into the hole, but an adjacent anti-retraction device remains depressed, preventing the bolt from being retracted unless the lock is turned.