Chains are usually made in one of two styles, according to their intended use:
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 makes the chain flexible in two dimensions.
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.
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 his or her way inside
Keychain, a small chain that connects a small item to a keyring
Lead shank (or "Stud chain"), used on difficult horses that are misbehaving
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