Door hinges are mechanical devices that allow doors to swing open and closed. They consist of two plates, called leaves, which are attached to the door and the door frame. A pin runs through the center of the leaves, enabling smooth movement. Hinges come in various types, including butt hinges, piano hinges, and concealed hinges, each serving different purposes and styles. The material of door hinges can vary, with common options being steel, brass, and stainless steel. The choice of material affects durability and appearance. Proper installation and maintenance of hinges are essential for ensuring that doors function correctly and last longer.