Split lock washers, also known as spring lock washers, are designed with a split at one point and bent into a helical shape. This causes the washer to exert a spring force between the fastener’s head and the substrate, creating more friction and resistance to rotation.Lock washers are specially designed to keep threaded fasteners from loosening. They prevent vibrations and some have external teeth to prevent rotation. These washers are often found in airplanes and in structural applications.