Pins are versatile fastening elements designed to perform functions such as locating, aligning, and securing components. Unlike threaded fasteners, pins are generally non-threaded and rely on interference fit, spring force, or locking mechanisms to secure parts in place. Common types include dowel pins for precision alignment, taper pins for load-bearing alignment, spring pins (roll pins) for shock absorption, and split pins (cotter pins) for locking assemblies. Their simple yet reliable design makes them indispensable in mechanical engineering, automotive, aerospace, and consumer applications.