Hinges are movable joints that connect two objects while allowing at least one of the objects to pivot. Hinges are used on doors, panels, gates, shutters, lids and any other object in which it is desirable to be connected while allowing it to swing.
There are many styles of hinges. Standard leaf hinge consists of two flat plates and barrel joined with a hinge pin, bullet hinges that have to be welded on, lift-off hinges easily separate allowing a door to be removed, and friction hinges hold prevent free-swinging of the hinge allowing a panel hold open.
Hinges are also available in a wide variety of materials, including steel, plastic, nylon, acrylic and stainless steel. They also come in a variety strengths. Plastic piano hinges are for light duty applications, while bullet and strap hinges are designed for heavier applications.