A hinge connects two bodies, usually one fixed and one moving, which allows angular movement along one axis while preventing any translation and rotation on the other two axes.
There are several types of hinges available each with intended application. Most hinges are derived from the butt hinge type. Hinges with an entirely different construction are geared continuous and living hinges.
The main components of hinges are leaves, knuckles (or barrels) and pin. From these components, characteristics can be defined such as leaf length, end play, pitch, and so forth.
Hinges are the usual weak points in structures. Design of hinges are determined by the load, end play, aesthetics, and environment. These factors must be balanced to produce the most suitable hinge.
Hinges are manufactured based on the hinge profile, material, cost, and available technology. The earliest metalworking processes to develop hinges is by forging and casting. As technology develops, mass production through extrusion, forming and milling are then used.