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How Does a Door Lock Work? Things You Should Know!

Fact checked by Teddy B.Miller

how does a door lock work

If you wonder “how does a door lock work?” here is the answer: when the door is locked, a part called the latch is partially in and out of the lock cylinder. The latch remains inside the lock cylinder if the door is unlocked. Only a key can disengage the latch and unlock the door.

Knowing how door locks work is necessary to install the lock yourself. After you familiarize yourself with the door locking mechanisms, assembling locks becomes an easy task.


Parts of a Door Lock


Before we tackle how locks work, you need to know first the parts of a door lock. Knowing each part’s features and functions will make understanding door locking mechanisms easier.

1. Cylinder

The cylinder is also known as the lock body because it contains the locking mechanism. Inside the cylinder are the spring-loaded pins that keep the lock secure. The spring-loaded pins won’t let the cylinder turn unless the correct key is inserted. If you want to learn more about lock cylinder, please click here for more details.

2. Bolt

The bolt or the latch is what prevents the door from opening. The latch is pulled out from the door jam whenever the doorknob is turned. The latch won’t disengage if the door is locked since the knob cannot be turned.

3. Strike Plate

The strike plate is a metal plate installed on the door’s jamb. It is positioned opposite the lock. It is also where the latch fits itself whenever the door is closed. Some strike plates have lips to keep the bolt in the correct position.

4. Keyway and Rotor

The keyway is the part of the lock where the key is inserted. On the other hand, the rotor is the part of the lock that turns when the correct key is inserted. It is located inside the cylinder of the lock.

5. Cotter Pin and Spring

The cotter pin aligns with the grooves in the key whenever the spring is under pressure. It also makes the rotor turn when the door is unlocked. On the contrary, the spring prevents the rotor from turning unless the correct key is inserted.

6. Spindle

A spindle is a metal rod that connects the two doorknobs located at each side of the door. The spindle rotates and retracts the latch whenever the doorknob is turned, thereby opening the door.

7. Doorknob or handle

The doorknob or handle provides grip for the owner of the house. The doorknob or the handle on the exterior part of the door is called the exterior knob or handle. The interior knob/handle is located inside. Most door knobs are made of brass.

How Door Locks Work

When a door lock is in the locked position, the latch is out of the lock cylinder and inside the strike plate. It ensures that the door won’t open unless the correct key has been inserted to open the door.

Each key has different patterns of ridges that will fit into a specific lock. On locking the door, key locks work by turning the cylinder. Once the cylinder is turned, it releases the spring to push the latch in a closed position.

The right key is also used to trigger the inside door lock mechanism to unlock the door. Once inserted in the keyway, the key will align the pins. This will turn the cylinder and unlock the door.

If you inserted the wrong key, the pins wouldn’t be aligned according to their proper position. Because of this, there would not be any gap between the upper and lower pins, and you cannot turn the lock’s cylinder.

If you want to know how a pin tumbler lock works, you can check out this video: “How does a Pin Tumbler Lock Work? It also includes the door lock mechanism diagram to show how the lock operates.

Frequently Asked Questions


1. How does a combination lock work?

Once the wheels are turned into the proper position, a gap between the top and bottom notches is formed. The part of the lock called the fence, which is on the wheels, falls into the gap, allowing the lock to open.

2. How does a power door lock work?

The actuator connects the car’s door handle to the opening when the latch is moved upward. When the latch is moved downward, the door handle and the unlock mechanism disconnect so the car door won’t open.


Answering “how does a door lock work?” will help you understand the door lock mechanism and its processes. Before you can master how the lock operates, you must first familiarize yourself with its parts and know their functions.

To understand more about the door lock, you can also check a door lock work diagram. It is crucial if you install locks frequently. Aside from that, fixing a lock is easier if you know how it works.

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