A washer is a thin plate (typically disk-shaped) with a hole (typically in the middle) that is normally used to distribute the load of a
threaded fastener, such as a
screw or
nut. Other uses are as a spacer, spring (
belleville washer, wave washer), wear pad,
preload indicating device, locking device, and to reduce vibration (
rubber washer). Washers usually have an outer
diameter (OD) about twice the width of their inner diameter (ID).