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Padlock

Simple three disc locking mechanism from a wooden box recovered from the Vasa, sunk in 1628

Medival lock in Kathmandu

A lock is a mechanical fastening device which may be used on a door, vehicle, or container, restricting access to the area or property enclosed. Commonly, it can be released by using a key or combination.

Securing one's possessions has long been a concern of people throughout the world. Beyond hiding the objects or constantly guarding them the most frequently used option is to secure them with a device. Early solutions included knots to either detect, like the Thief knot, or hamper, like the Gordian knot.

Wooden locks and keys were in use as early as 4,000 years ago in Egypt [1]. The first known lock with a key was a pin lock where a cylinder of wood with a hole drilled through its axis was the key. The length of the cylinder was the critical factor. It was strung on a rope hanging out of a hole in a door. Then the key was inserted into the hole and the rope pulled to push the cylinder to push the bolt the correct distance. To lock the door just pull on the rope to extract the key cylinder and simultaneously pulling the bolt closed. This type of lock is still in use in certain parts of the world. A danger of this lock was a vandal could push the rope into the hole; an ancient equivalent of putting glue into a lock.

Early improvements in pin locks included increasing the number of pins to increase security, and changing the orientation of the pins to allow the key to provide the unlocking force instead of a rope. Thus establishing the principles of the modern Pin tumbler lock.

Next was developed a warded lock that is still used in modern times when the security required is not high and cost is a significant factor. It is the first lock design to have a key recognizable to a modern western person. Lock puzzles were used to obscure the locking mechanism or even provide a nonfunctioning lock for the thief to waste time on.

• Robert Barron patented a double-acting tumbler lock in 1778, the first reasonable improvement in lock security.
• Joseph Bramah patented the safety lock in 1784. It was considered unpickable for many years.
• Jeremiah Chubb patented his detector lock in 1818. It won him the reward offered by the Government for a lock which could not be opened by any but its own key.
• James Sargent invented the world's first successful key-changeable combination lock in 1857. His lock became popular with safe manufacturers and the United States Treasury Department. In 1873, he patented a time lock mechanism, the prototype for those used in contemporary bank vaults.
• Samuel Segal invented the first jimmy proof locks in 1916.
• Harry Soref founded the Master Lock Company in 1921 and patented an improved padlock in 1924 with a patent lock casing constructed out of laminated steel.
• Linus Yale, Sr. invented a pin tumbler lock in 1848.
• Linus Yale, Jr. improved upon his father's lock in 1861, using a smaller, flat key with serrated edges that is the basis of modern pin-tumbler locks. Yale invented the modern combination lock in 1862.

A type of padlock side view.

Door with two locks, one in the doorknob and a separate deadbolt.

Locks may be entirely mechanical, or electromechanical. They may be operated by turning some form of removable key, by keying or dialling in a combination which directly or via electromechanical means operates the lock, with some form of magnetic or other card reader, or by moving a part on a safety lock intended to prevent accidental operation rather than to prevent unauthorised access.

• Bicycle lock
• Child safety lock
• Combination lock
• Cruciform (or Zeiss) lock
• Cylinder lock
• Deadbolt
• Disc tumbler lock
• Door chain
• Electronic lock
  • Magnetic lock
  • Electric strike
• Lever tumbler lock
  • Chubb detector lock
  • Protector lock
• Padlock
• Pin tumbler lock
  • Tubular pin tumbler lock
• Wafer tumbler lock
• Warded lock
• 5 Lever Lock
• Keycard lock
• Rim lock
• Magnetic keyed lock

• Lock picking
• Locksmithing
• Physical security

• Locksmith & Locks Blog
• History of Locks from the Chubb website
• Locksmithing Throughout the Ages
• History of Locks from J&M Lock
• The History of Locks
• General Information

• Phillips, Bill. (2005). The Complete Book of Locks and Locksmithing. McGraw-Hill. ISBN 0071448292.