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How Does a Key Work?

Keys and locks are a security devices that combine complexity with simplicity.

Here are the basic principles of how a key functions within a lock:

Basic Parts of a Lock


The part of the lock that turns to open the lock when the correct key is inserted.


The opening in the cylinder where the key is inserted.


Small metal pieces that block the cylinder from turning unless the correct key is inserted. These consist of upper pins and lower pins.

Shear Line

The separation line between the cylinder and the lock housing. The lock can only be opened when all the pins are aligned at this line.

How a Key Works

The process of how a key operates begins with inserting the key into a lock’s keyhole. The design of the key includes grooves that specifically made to match the lock’s configuration. As the key is pushed into the keyhole it moves the lock’s pins.

The correct key is shaped to push these pins to a precise height aligning them at the shear line. This alignment removes the barrier that prevents the cylinder from turning. 

Once the pins are aligned there’s nothing to stop the cylinder from turning which unlock it.

Security Features

Complex Key Profiles

More complex designs with unique grooves make it harder to pick a lock.

Security Pins

These are specially designed pins that make the lock more difficult to pick.

Master Key

This system allows multiple different keys to operate with the same lock, commonly used in commercial buildings.