A car door latch operates using a series of levers and other parts that work together to secure your doors. Most door latches consist of a handle that is attached to an actuator arm positioned inside the door frame itself. This arm will pull directly or indirectly on the latch lever you can see on the inside panel of the door itself. When this latch is pulled back or released, the door can be pulled open. When it is not in use, the latch automatically closes. This is a safety measure in place on all cars.
Latch and Post
A door latch has a small piece of metal that latches over a U-shaped metal bolt on your door frame. The latch is a simple metal tongue that slides back on a spring-loaded swivel. When the door is closed, this lever swings back over the U-shaped bolt it lines up with on the door frame. Then it slides closed over the U-shaped bolt. As explained above, the door latch handle can release this lever so the door can be opened again, but in a normal situation the latch is always closed over the bolt. This is similar to the latch and post design used on many house gates.
Pulling on the door handle releases this latch and lets the door be opened, but the lock must be released to allow this latch to open. If the lock on the door is set, the latch will not release, because the door handle will not engage the release arm that is connected to the lever, and the car door will not open. Today, locks are set by electronic actuators inside the car. They are quite similar to the old-fashioned locks, with motors driving the positioning of the locking arms. These locking arms engage and disengage the door latch to release locks on the door.