What is the purpose of the hinge pin in a door assembly?

The hinge pin in a door assembly serves a critical function by allowing the door to pivot open and closed. This pivoting action is essential for the door's operation, enabling it to swing smoothly around the hinge axis. By connecting the two components of the hinge—the leaf attached to the door and the leaf attached to the frame—the hinge pin allows for easy access through the doorway while ensuring stability and alignment in the door's movement.

Other possible functions, such as providing a decorative finish or strengthening the door against impacts, do not accurately describe the primary role of the hinge pin. While some door hinge designs may exhibit decorative elements, the main purpose is functionality rather than aesthetics. Strengthening against impacts is more related to the material and construction of the door itself rather than the hinge pin's role. Similarly, the locking mechanisms of a door are not assisted by the hinge pin; those functions are typically performed by separate components designed specifically for locking purposes. Thus, the pivoting function provided by the hinge pin is key to the effective use of any door assembly.