Combination lock facts for kids
A combination lock is a special type of lock. You open it using a secret set of numbers or letters, not a key.
There are two main kinds. Some have a spinning dial, like old safes. You turn the dial to certain numbers to unlock them. Others have a keypad, like a phone. You just type in your secret code.
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How Mechanical Combination Locks Work
Mechanical combination locks have a spinning dial. Inside, they usually have three round discs. These discs are connected in a clever way. When you turn the dial, the discs spin too.
To open the lock, you turn the dial in a special order. You might turn it clockwise to the first number. Then, you turn it counter-clockwise past the first number to the second number. Finally, you turn it clockwise again to the third number. This lines up the discs just right.
You often see these locks on safes and padlocks. They are not common on house doors. This is because it takes a bit of time to dial the numbers. Usually, the secret code for these locks is set at the factory. It's often hard or impossible to change it later.
How Electronic Keypad Locks Work
Electronic combination locks use a keypad. This keypad looks a lot like the numbers on a telephone. You enter your secret code one number at a time. After you type the correct code, a small motor inside the lock opens it.
These locks are popular for safes and doors. However, you almost never see them on padlocks. Electronic locks need power to work. They usually run on batteries or are plugged into electricity.
Sometimes, these locks have a backup key. This is helpful if the batteries die or the electronics stop working. But many safe locks do not have a key backup. This is because a keyhole could be picked open by a thief. A great thing about most electronic locks is that you can easily change the combination yourself.
Why Use Combination Locks?
Combination locks have some good points. You don't need to carry a key, so there's no key to lose! Also, if there's no key backup, these locks are very hard to pick open. As long as you remember your secret code, you won't get locked out.
Challenges with Combination Locks
Mechanical combination locks can be tricky at first. People sometimes forget to pass the first number when dialing the second one. Or they might turn the dial the wrong way.
For electronic locks, the batteries can die. If this happens, the lock won't open until you replace them. With any combination lock, a thief might try to watch you enter your code. This is called "shoulder surfing." They can then use your code to open the lock. On electronic keypads, worn-out buttons might even show which numbers are part of the combination.
Images for kids
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A Wordlock letter combination lock.
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Exploded view of the rotating discs. The notches on the disc correspond to the numerals in the correct combination. In this case, the combination is 9-2-4.
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The discs are mounted on one side of the lock, which may in turn be attached to the end of a chain or cable. The other side of the lock, or the other end of the cable, has a pin with several protruding teeth.
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When the toothed pin is inserted and the discs are rotated to an incorrect combination, the inner faces of the discs block the pin from being extracted.
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A single-dial padlock by Master Lock.
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Stoplock Dismantled.jpg
The component parts of a Stoplock combination padlock.
See also
In Spanish: Cerradura de combinación para niños
