Chain Facts for Kids

A broad metal chain made of torus-shaped links.

A metal chain with diamond-shaped link pins.

Roller chains.

A chain is a series of connected links which are typically made of metal. A chain may consist of two or more links.

Those designed for lifting, such as when used with a hoist; for pulling; or for securing, such as with a bicycle lock, have links that are torus shaped, which make the chain flexible in two dimensions (The fixed third dimension being a chain's length.)
Those designed for transferring power in machines have links designed to mesh with the teeth of the sprockets of the machine, and are flexible in only one dimension. They are known as roller chains, though there are also non-roller chains such as block chain.

Two distinct chains can be connected using a quick link which resembles a carabiner with a screw close rather than a latch.

Uses for chain

Part of The Hudson River Chain at West Point

Uses for chain include:

Chain of office, collar or heavy gold chain worn as insignia of office or a mark of fealty in medieval Europe and the United Kingdom
Decorating clothing, some people wear wallets with chains connected to their belts, or pants decorated with chains
Figaro chain, a decorative style of chain most often seen in men's jewelery
Omega chain, a pseudo-chain where the 'links' are mounted on a backing rather than being interlinked
Jewelry chain, many necklaces and bracelets are made out of small chains of gold and silver

Bicycle chain, transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it
Chain drive, the main feature that differentiated the safety bicycle
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 an endless chain has positioned on it circular discs
Chainsaw, portable mechanical, motorized saw using a cutting chain to saw wood
Flat chain, form of chain used chiefly in agricultural machinery
Ladder chain, a light wire chain used with sprockets for low torque power transmission
O-ring chain, a specialized type of roller chain
Roller chain, the type of chain most commonly used for transmission of mechanical power on bicycles, motorcycles, and in industrial and agricultural machinery
Timing chain, used to transfer rotational position from the crankshaft to the valve and ignition system on an internal combustion engine, typically with a 2:1 speed reduction.

Ball and chain, phrase that can refer to either the actual restraint device that was used to slow down prisoners, or a derogatory description of a person's significant other
Bicycle lock (or "Bicycle Chain"), lockable 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 zig zag 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
Leg iron chains (fetters), an alternative to handcuffs
Security chain, chain with square edges to prevent cutting with bolt-cutters

Anchor cable, as used by ships and boats, in British nautical usage it is a cable, not a chain
Chain steam shipping
Chain-linked Lewis, lifting device made from two curved steel legs
Curb chain, used on curb bits when riding a horse
High-tensile chain (or "Transport chain"), chain with a high tensile strength used for towing or securing loads
Jack chain, a toothed chain used to move logs
Lead shank (or "Stud chain"), used on horses that are misbehaving
Pull switch, an electrical switch operated by a chain
Rigid chain actuator, a type of chain that only bends in one direction, allowing it to operate under compression
Snow chains, used to improve traction in snow
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 cisterns no longer work like that, the phrase "pull the chain" is still encountered to mean "flush the toilet".

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-shot, a type of ammunition for a cannon, used to inflict damage to the rigging of a sail vessel in naval warfare
Chain weapon, a medieval weapon made of one or more weights attached to a handle with a chain

Chains can also be used as a percussion instrument for special effects, such as in Schönberg's Gurre-Lieder and Janáček's
Keychain, a small chain that connects a small item to a keyring
Chain sinnet, a method of shortening a rope or other cable while in use or for storage
Chain stitch, a sewing and embroidery technique