Locks have been around for thousands of years. Probably as long as there have been valuables that people wanted to protect, locks — in some form — have been there to keep things secure.
You probably encounter all sorts of locks every day. From combination locks on school lockers to deadbolt locks on front doors, locks are all around us.
Today there are many different kinds of locks. Some are very simple locks that open with a key or a combination of numbers.
Others are extremely complicated locks that open with fingerprints or special electronic keycards. Today’s locks feature many different types of mechanical and technological systems to increase security.
To get a basic understanding of how locks work, let’s take a look at two common types of locks: combination locks and pin-and-tumbler locks. These common locks are the ones you’re most likely to see on a day-to-day basis.
Combination locks can be found in all sorts of places. From gym lockers to shed doors to secret diaries, combination locks allow their contents to be accessed only by those who know the secret combination of numbers that will open the lock.
A typical combination padlock, for example, contains a wheel pack. The wheel pack contains one wheel for each number in the combination.
Each wheel in the wheel pack has a small tab — called a “wheel fly” — on each of its sides. As you turn the combination dial, a spindle that extends through the wheel pack turns a drive cam.
As the drive cam turns, an attached drive pin makes contact with the wheel fly on the nearest wheel. As you continue to dial in the correct combination, the wheel fly on each subsequent wheel makes contact until all the wheels are spinning.
When you get to the last digit of the combination, all wheels will be lined up perfectly. Notches cut into each wheel will also be aligned. These notches form a gap that will allow the lock to release and open.
Pin-and-tumbler locks are different because they require a key to unlock them. Basic pin-and-tumbler locks have several spring-loaded pins inside a series of small cylinders.
When the right key slides into a pin-and-tumbler lock, the pointed teeth and notches on the blade of the key allow the spring-loaded pins to move up and down until they line up with a track called the “shear line.” When the pins align with the shear line, the cylinder can turn, and the lock will open.
If you don’t have the right key, one or more of the pins will remain in the way of the shear line. This will prevent the cylinder from turning, and the lock will remain closed.