Grades 3–5 · Machines
How does a door latch keep a closed door in place?
A spring latch is a small sliding bolt at the edge of a door. A spring pushes its nose outward. In the frame, a strike plate surrounds an opening that can receive the latch when the door closes.
In the diagramA spring latch enters a matching frame openingdoorframehandle withdraws latchA sloping nose retracts as the door closesThe spring extends the nose when the receiving opening lines up.
As the door swings shut, the latch’s sloping face meets the strike plate. That contact pushes the latch inward against its spring. Once the nose reaches the opening, the spring pushes it outward again into the frame.
The extended latch blocks the door from simply swinging open. Turning the handle uses an internal mechanism to withdraw it, clearing the opening so the door can move. A lock, where present, controls access to that release mechanism or another securing part.
A door may fail to latch if the nose and opening do not line up, even when the spring works. The useful result depends on the relationship between two structures: a moving piece on the door and a fixed place in the frame.
About this explanation
Starting knowledge: Recognize a door, its frame and a part sliding in and out.
Sources
- Schlage — Parts of a door lock and door hardware terms defined