A piece of wood or metal, commonly wedge-shaped, used for fastening together parts of a machine or structure. It is driven into an opening through one or all of the parts. [See Illust.] In the United States a cotter is commonly called a key.

To fasten with a cotter.

fastener consisting of a wedge or pin inserted through a slot to hold two other pieces together

split pin with spreadable ends.

A bolt that is placed through a slot to hold something together.