How do locks work?

For the last 4000 or so years, humans have used a variation of locks to secure their homes and valuables. It all started in ancient Egypt, where the first locks were developed, made entirely from wood. Over the years, we have continued to innovate our locking technology, with particular success during the Industrial Revolution. During this time, locks became much more advanced and intricate, with the inventions of the Bramah and double-acting locks, and a huge surge in the production of metals, particularly steel. So, how do locks work?

Obviously different locks work in different ways.

Photo by marcos mayer on Unsplash

Pin-tumbler locks

One of the most common lock types, commonly found in padlocks and doors, is the cylinder pin-tumbler lock. It is said to have been created by American inventor Linus Yale Sr. in 1848, but the locks found in ancient Egypt thousands of years before were actually strikingly similar to the “Yale lock”. The modern pin-tumbler lock consists of a metal cylinder within sturdy, wherein a series of metal pins hold the lock closed. There are two sets of pins, the upper and lower pins, that interact with each other, and are held up with springs.


When the correct key is inserted, the grooves of the key will correspond to the levels of the metal pins, adjusting them to a height wherein the upper pins sit above the edge of the cylinder and no longer lock into its housing. Then, when you turn the key, there’s nothing stopping the cylinder from rotating, so the lock opens.

Combination locks

Combination locks are found all over, from lockers, to bike locks, to safes. Most locks of this kind use a wheel pack, a set of wheels that are programmed to unlock when a certain combination is entered. The amount of wheels in the pack are determined by the amount of numbers in the combination; each wheel is set to ‘remember’ a number, so there is essentially one wheel per number.

Basically, when you spin to the correct number in the combination, the notches on the wheels all line up and form a gap. On a padlock, this gap allows the hasp of the lock to release. In a safe, the ‘fence’, a piece which rests above the wheels, will fall into said gap under it’s own weight, allowing the bolt to slide freely past and the safe to open.

For the most part, other locks operate in similar ways to the two listed above, with slight variations in the hardware and the pieces within the lock. Digital locks do differ from mechanical ones drastically, but the way they work is more to do with electronics and software than physical mechanisms like the ones mentioned above.

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