Custom door hinge factory right now: Piano Hinge – Also known as a continuous hinge, a piano hinge is a long hinge designed to provide continuous support along the entire length of the door. It is often used for the lids of large chests or toy boxes – or the lids of upright pianos, where the hinge takes its name from. Piano hinges can either be mortised into the lid and frame, hidden when the lid is closed, or mounted on a surface as a type of strap hinge.It’s also good for fold-down workbenches and desks, cabinet doors and storage …