Located inside the latch casing. It provides the tension that pushes the latch bolt back out into the locked position after you open the door.
If your door isn't working, refer to the diagram to identify the culprit: diagram of door lock
| Lock Type | Diagram Differences | |-----------|----------------------| | | Shows separate deadbolt cylinder & thumb turn; no spring-loaded latch. | | Smart Lock (Electronic) | Adds battery, motor, circuit board, keypad/sensor, and electronic clutch. | | Mortise Lock | Large rectangular body inside pocket cut into door; shows levers, set screws, and multiple bolts. | | Rim Lock | Surface-mounted on door interior; simple deadbolt + latch in one visible case. | Located inside the latch casing
Door locks generally fall into two categories based on how they are installed in the door: and Mortise . Parts Of A Door Lock: Names & Diagrams - Panda Windows | | Smart Lock (Electronic) | Adds battery,