Achain[1] is aserial assembly of connected links typically made of metal, with an overall character similar to that of arope in that it is flexible andcurved incompression, butlinear, rigid, and load-bearing intension. A chain may consist of two or more links. Chains can be classified by their design, which can be dictated by their use:
Those designed for lifting, such as when used with ahoist; for pulling; or for securing, such as with abicycle lock, have links that aretorus-shaped, which make the chain flexible in twodimensions (the fixed third dimension being a chain's length). Small chains serving asjewellery are a mostly decorative analogue of such types.
Those designed for transferring power in machines have links designed to mesh with the teeth of thesprockets of the machine, and are flexible in only one dimension. They are known asroller chains, though there are also non-roller chains such asblock chains.
Bicycle chain, type of roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. The chain is made up of a number of rigid links that are hinged together by pin joints to provide the flexibility needed to wrap around the bicycle's gears.
Chain gun, type of machine gun that is driven by an external power source, sometimes connected by a chain, to actuate the mechanism rather than using recoil
Chain pumps, type of water pump where a loop of chain inset discs is passed around then through a tube submerged in liquid
Timing chain, used to transfer rotational position from the crankshaft to the valve and ignition system on aninternal combustion engine, typically with a 2:1 speed reduction.
Belly chain (or waist chain), a physical restraint worn by prisoners, consisting of a chain around the prisoner's waist, to which the prisoner's hands are chained or cuffedPrisoner in belly chain
Chain boom, large chains used to exclude warships from harbors and rivers
Chain link fencing, fencing that utilizes vertical wires that are bent in a zigzag fashion and linked to each other
Chain mail, a type of armor consisting of small metal rings linked together in a pattern to form a mesh.
Door chain, a type of security chain on a door that makes it possible to open a door from the inside while still making it difficult for someone outside to force their way inside
Gang transport chain, a chain used to shackle two or more inmates together for transport or work outside the facility, forming achain gang
H-style restraints, a combination consisting of handcuffs on a belly chain with a connector chain running down to a set of leg irons
Leg iron chains (fetters), an alternative to handcuffs
Prisoner transport restraints, a combination which consists of a pair of handcuffs attached by a longer chain to a pair of leg irons
On chain-linkedhandcuffs, the cuffs are held together by a short chain
Lavatory chain, the chain attached to the cistern of an old-fashioned W.C. in which the flushing power is obtained by a gravity feed from above-head height. Although most cisterns no longer work like that, the phrase "pull the chain" is still encountered to mean "flush the toilet".
Rigid chain actuator, a type of chain that only bends in one direction, allowing it to operate under compression
Chain gun, type of machine gun that is driven by an external power source, sometimes connected by a chain, to actuate the mechanism rather than using recoil
Roller chain, the type of chain most commonly used for transmission of mechanical power on bicycles, motorcycles, and in industrial and agricultural machinery
Self-lubricating chain, type of chain that uses a bush to continually lubricate the chain
Silent chain, a type of chain in which the links engage the sprockets similarly to gear teeth
Stud link chain, a type of chain with metal between the sides of each link, keeping the attached links in place. This helps prevent bunching when the chain is run out from a storage bin, as for use in anchoring ships.
Short link chain, a chain where the gap between attached links is small relative to thickness.
Several methods are available to connect chain ends to each other or to other objects, and to apply a load to a chain away from the ends. These methods are usually specific to the type of chain, and must be of the correct size.
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The earliest uses of the chain date to Ancient Egypt (between 3150-332 BC)[4], where it was used for moving water in the elevator systems. Such systems were also used in China, by the Han Dynasty (202 BC-220 AD), to move water around rice terraces.
The metal link chain has been in use since at least 225 BC.[5]
^As early as 225 BC, chain was used to draw a bucket of water up from a well. This very early bucket chain was composed of connected metal rings.Tsubakimoto Chain Co., ed. (1997).The Complete Guide to Chain. Kogyo Chosaki Publishing Co., Ltd. p. 240.ISBN0-9658932-0-0. p. 211. Retrieved17 May 2006.
^The use the metaphor of chains to symbolize the oppression of the proletariat under capitalism.Howard, James."The Communist Manifesto Symbols: Chains".LitCharts LLC. Retrieved20 October 2025.
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