lock

lock

[lok]
lock, air: see air lock.
lock, canal, stretch of water enclosed by gates, one at each end, built into a canal or river for the purpose of raising or lowering a vessel from one water level to another. A lock may also be built into the entrance of a dock for the same purpose. When the ship is to be raised to a higher level, it enters the lock and a gate is closed behind it. Water is let into the lock until its level equals that of the water ahead. The forward gate is then opened, and the ship progresses on the higher level. The procedure is reversed when the vessel is to pass from a higher to a lower level. As many locks as necessary are used in a given waterway. Most modern locks are made of concrete, although some have walls of steel-sheet piles or floors of natural rock or sand. The mitre gate, frequently used in the United States, consists of two swinging sections forming an arc or shallow V, with the apex pointed toward high water so that water pressure keeps both sections tightly sealed when closed. Another type of gate in common use consists of one piece of sheet steel that slides across the entrance to the lock on rollers or is lifted into the air or sunk underwater. The gates of most locks are operated by hydraulic or electric power. Water is poured into or out of locks through culverts built into the masonry structure of the lock walls. Among well-known locks are those of the Panama Canal.

Device for igniting the powder in a firearm such as a musket. Developed circa 1515, the wheel lock struck a spark to ignite powder in the pan of a musket by means of a holder that pressed a shard of flint or a piece of iron pyrite against an iron wheel with a milled edge; the wheel rotated and sparks flew. The principle was used in the design of the flint-and-wheel cigarette lighter. Seealso flintlock.

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A cylinder lock's tumbler consists of a series of pins arranged in pairs. The pins are elipsis

Mechanical or electronic device for securing a door or receptacle so that it cannot be opened except by a key or a code. The lock originated in the Middle East; the oldest known example was found near Nineveh. Possibly 4,000 years old, it is of the pin tumbler type, otherwise known as an Egyptian lock. The Romans were the first to use metal locks and to make small keys for them. They also invented wards, projections in the keyhole that prevent a key from turning unless it has slots that avoid the projections. Probably the most familiar lock today is the cylinder lock, a pin tumbler lock opened by a flat key with a serrated edge; the serrations raise pins in the cylinder to the proper heights, allowing the cylinder to turn. Also common are the unit lock, housed within a rectangular notch cut into the edge of a door, and the mortise lock, housed in a mortise cut into the door edge, the lock mechanism being covered on both sides. Other types include lever and combination locks. Electronic locks that open with a magnetic card key are popular for banks, hotel rooms, and offices.

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Lock may refer to:

Mechanical devices

  • Lock (device), a mechanical device used to secure possessions
  • Lock (firearm), the ignition mechanism used on early projectile weapons
  • Lock (water transport), an enclosure in a navigable canal or river which enables ships and boats to pass between sections of the waterway at different levels

Technology

  • Lock (computer science), a bookkeeping object associated with a piece of data that is used to serialize concurrent access
  • Lock (database), a feature used when multiple users access a database concurrently
  • Lock (weapons guidance), an indication the missile seeker system has a suitable or adequate acquisition fix to hit successfully if launched

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