For locks on a river or canal, see Lock (water transport)
An electronic lock on a door

A lock is a fastening device: a thing which keeps people from opening something, such as a door or a box. Locks can be released by an object called a key, or by an electronic card, or by secret information, like a code. The verb to lock means to set the lock so the door or object is closed. A person who works on locks is called a locksmith.

Types of lock mechanisms

A key lock is a lock that uses a key (a piece of metal with teeth like a little saw) to open it. Someone must put the key in the lock and turn it to open the lock. This lock is used in doors and locks for boxes. Key locks can be defeated by picking them.

A combination lock is a lock that uses a dial (a knob with numbers all around it) to open it. Someone must turn the dial to the right numbers in the right order. This is called the "combination." This lock is used on safes and locks for bicycles.

An electronic lock is a special lock that can only be opened with a message from a computer. This message can be stored in a computer chip on a card (called a "key card" or "security card"). Or it can be made by a computer looking at someone's fingerprint or eye.

Time locks are used in banks. They prevent anyone opening the vault until a preset time. This defeats burglary attempts when the bank is closed.

Types of lock

Padlocks are probably the most common type of lock. They are opened either with a key or a combination. The best way to break them is to snap the hoop with a long-handled bolt cutter.

Pin tumbler locks, commonly called 'Yale locks', are very common for fastening doors. They were indeed invented by Linus Yale Jnr in the 1860s.

Deadbolts are locks which cannot be moved to the open position except by rotating the cylinder.

Spring latch lock. The common door latch which locks when you pull the door closed. It is much less secure than a deadbolt lock, but more convenient.


No lock is completely safe, though some are safer than others. Locks can be defeated by brute force or by lock picking. The most common brute force tool is the crowbar, commonly called (UK) a jimmy or jerry or (US) a wrecking bar.

Picking involve tools such as pin-tumbler lock picks, skeleton keys, bump keys, pick guns etc. Carrying these tools, especially after dark, is an arrestible offence in most countries except if the owner is a registered locksmith.[1]


  1. Lockpickguide.com [1]