Hinges include two leaves joined by a knuckle that holds them together. They fasten to frames and other structures, allowing doors to open and close freely. Butt hinges have one leaf that mounts onto a door or lid and the other to the frame. Electrified hinges are wired to power locks, exit devices, and access control systems. Piano hinges have a central pin with leaves on both sides that run the entire length of the door or lid to distribute weight evenly for added support. Lift-off hinges stay in place and allow doors to be lifted off, making room for deliveries or similar needs. Pivot hinges attach to the bottom and top of doors, distributing the weight more evenly to support large and heavy doors. Spring hinges have a built-in spring that automatically closes the door. Concealed hinges install flush with the door and frame so they’re not visible, improving aesthetic appearance. Specialty hinges suit the needs of specific industrial and residential applications.