Chain

A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A chain may consist of two or more links. Chains can be classified by their design, which can be dictated by their use: 
Two distinct chains can be connected using a quick link, carabiner, shackle, or clevis.
Load can be transferred from a chain to another object by a chain stopper
Uses for chain.
Uses for chain include:
Connections.
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.
Invention.
The metal link chain has been in use since at least 225 BC.
Symbolism.
The prevalent modern symbolism is oppression, due to the use for a mechanical restriction of the liberty of a human or animal.
Chains can also symbolize interconnectivity or interdependence. Unicode, in versions 6.x, contains the , which may show chain link(s). It may also denote a hyperlink.