A piano hinge is a long, narrow hinge that is used to attach two objects together in a way that allows for a smooth, hinged movement. Piano hinges are often used on pianos, hence the name, but they are also used on other types of products such as windows, doors, cabinets, and furniture. Piano hinges are made of steel or aluminum and are designed to be strong and durable. They are usually very thin and are mounted in a way that minimizes the use of screws or other fasteners, resulting in a smooth, seamless movement. Piano hinges can be used on objects of different sizes and weights, depending on the strength of the hinge and the specific needs of the product.