Have you ever thought about how often you come across locks on a day to day basis? From locking the bathroom door to unlocking filing cabinets, we use locks and keys all the time. There are a surprising number of lock and key mechanisms, each working in different ways. If you’ve ever wondered how locks work, then read on for our guide that should answer all your questions.

We’ve broken up the lock types by the type of key you use to access it as the key pretty much defines how the lock works.

Flat Key

A flat key is most often used in door locks, in conjunction with a “pin tumbler lock”.

A pin tumbler lock is made up of an outer casing with a cylindrical ‘plug’ in the middle. The plug needs to rotate for the lock to open, but it can’t without the key!



The front of the plug has a slot for the key to go into – this is called the keyway. The top of the plug and the outer casing have vertical holes, with two pins of various lengths dropped in on top of each other. The pins block the plug from moving.

When the corresponding flat key is inserted, the pins will be lifted to the shear line where the outer casing and the plug meet. There, the pins and the shear line will align exactly, and leave the plug open to rotate, and open the lock.

This type of lock is vulnerable to lock-picking however, as there are a number of methods that can be used to spring it.

Round Key

This type of key is commonly used on bike locks, elevators and coin-operated devices such as launderette washing machines.

These locks are known as “tubular pin tumbler locks”, and they are very similar to a standard pin tumbler lock. Instead of having the pins in a line, they are in a circle. When the pins line up with the shear line, the plug is free to move and open the lock.



They are generally considered to be more resistant to lock-picking than standard locks, though certain tubular locks, like bike locks, can be forced open with a big pen.


Instead of a physical key, you use a sequence of letters or numbers to open the lock. This is often used with padlocks, bike locks and key cabinets.

The lock will have a rotating dial, with numbers or letters printed on the front. On the inside, each character will have a notch (or not). Once aligned, the pins on the other side of the lock can pass through, opening the lock.



Depending on the number of digits, there are tens of thousands of options for your code, preventing a thief from guessing your combination just by chance. However, be wary of people watching over your shoulder when you enter your code.

Smart Key

An alternative door locking system, it is often used for shared buildings, like offices or blocks of flats.

The key is not your traditional physical one, but instead a key fob or even a smartphone. They are configured to send the right message to the lock to tell it to open or close. Smartphone keys work wirelessly on Wi-Fi, Bluetooth or Z-Wave, allowing you to lock or unlock remotely. You can even grant access to other people by sending a “virtual key” to their phone, allowing you to monitor who is locking or unlocking the door via a smartphone app.

The benefits of smart security allow your home to be connected via a singular system, making it easy to control and maintain. One of the main vulnerabilities of a smart lock however is that it is open to skilled hackers, but the likelihood that a hacker would choose to spend their time trying to get into a smart-locked home is slim.

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All images designed by Wapcaplet and used under the Creative Commons Attribution-Share Alike 3.0 Unported license.

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