A lock washer is a metal disc with a hole in the center intended to be placed between a fastener and the work surface. The lock washer has sharp edges which bite into the fastener head and work surface to prevent them from turning once they have been tightened down. This prevents loosening of the fastener due to vibration or other mechanical forces. When used in a nut and bolt configuration, the lock washer is typically used with the nut side. When used with a tapped hole, there is no nut and the lock washer is placed under the bolt head. Because the lock washer bites into the work surface, it is also used for electrical grounding purposes. The bite ensures an excellent conductive connection between the fastener or crimped ring terminal and the work surface because it penetrates corrosion, paint, or other defects which could degrade the connection.