What Is a Door Strike Plate?

The flat metal plate screwed into the door jamb, with a rectangular opening that the spring latch bolt drops into when the door closes. Its square inner edge is what holds the door shut, and its curved lip is what lets the beveled bolt ride in without turning the knob. Because the door hangs on hinges that loosen and a frame that settles, the plate and the bolt slowly drift out of line, which is why a door that once clicked shut starts drifting open.

Diagnosing the drift takes a smear of lipstick on the bolt and one close of the door. The mark on the plate shows whether the bolt is landing high, low, or short. A miss under 1/8 inch is filed out of the opening with a half-round file. A bigger miss means plugging the old screw holes with glued toothpicks and resetting the plate, or driving a 3-inch screw through the top hinge to lift a sagging door back into position.