How Does A Lock Work

What is a lock? How does it work? What am I doing?

What is a lock:

A lock is a mechanical fastening device which may be used on a door, vehicle, or container. Commonly, it can be released by using a key or combination.*

How does it work:

There are many types of locks, that work in various methods.
The different types of locks are:

  • Pin tumbler (the most common in use in modern times)
  • Lever (usually found in the UK and the most common on handcuffs)
  • Waffer (found mostly on display cases and filing cabinets)
  • Tubular (bike locks and vending machines)
  • Warded (found usually with cheap padlocks)
  • Disc (Abloy is the best known)

Since the Pin Tumbler lock is the most common lock you will come across and for the purpose of this article we will be focusing on it.

Pin tumbler lock



The basic principles of the pin tumbler lock may date as far back as 2000 BC in Egypt; the lock consisted of a wooden post affixed to the door, and a horizontal bolt that slid into the post. The bolt had vertical openings into which fitted a set of pins. These could be lifted, using a key, to a sufficient height to allow the bolt to move and unlock the door.

Inventor Linus Yale, Sr. patented a cylindrical pin tumbler lock in 1848, a design which was further improved and patented by his son, Linus Yale, Jr., in 1861. Yale, Jr.'s design is very similar to pin tumbler locks manufactured today.


The pin tumbler is commonly used in cylinder locks. In this type of lock, an outer casing has a cylindrical hole in which the plug is housed. To open the lock, the plug must rotate.

The plug has a straight-shaped slot known as the keyway at one end to allow the key to enter the plug; the other end may have a cam or lever which activates a mechanism to retract a locking bolt. The keyway often has protruding ledges which serve to prevent the key pins from falling into the plug, and to make the lock more resistant to picking. A series of holes, typically five or six of them, are drilled vertically into the plug. These holes contain key pins of various lengths, which are rounded to permit the key to slide over them easily.

Above each key pin is a corresponding set of driver pins, which are spring-loaded. Simpler locks typically have only one driver pin for each key pin, but locks requiring multi-keyed entry, such as a group of locks having a master key, may have extra driver pins known as spacer pins. The outer casing has several vertical shafts, which hold the spring-loaded pins.

When the plug and outer casing are assembled, the pins are pushed down into the plug by the springs. The point where the plug and cylinder meet is called the shear point. With a key properly cut and inserted into the groove on the end of the plug, the pins will rise causing them to align exactly at the shear point. This allows the plug to rotate, thus opening the lock. When the key is not in the lock, the pins straddle the shear point, preventing the plug from rotating. Sets of locks with a master key will have one set of shear points that are identical to the others in the set and one set that is unique to that specific lock.

Without a key in the lock, the driver pins (blue) are pushed downwards,
preventing the plug (yellow) from rotating.
When the correct key is inserted, the gaps between the key pins (red)
and driver pins (blue) align with the edge of the plug (yellow).
With the gaps between the pins aligned with the shear line,
the plug (yellow) can rotate freely.

Picking the pin tumbler: What are you trying to accomplish

<and FYI
"The license Wikipedia uses grants free access to our content in the same sense as free software is licensed freely. This principle is known as copyleft. That is to say, Wikipedia content can be copied, modified, and redistributed so long as the new version grants the same freedoms to others and acknowledges the authors of the Wikipedia article used (a direct link back to the article satisfies our author credit requirement). Wikipedia articles therefore will remain free forever and can be used by anybody subject to certain restrictions, most of which serve to ensure that freedom." this is what makes this easier!!!!!!! omega >

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-Share Alike 2.5 License.