Lock Washers (or more properly, helical spring lock washers) look like they are broken, but are actually very short coil springs. In use, they increase a bolt’s clamping force (per unit of applied torque) and help prevent loosening due to vibration, among other things. In general, if a bolted joint is supposed to clamp materials together, adding a lock washer is worthwhile. Lock washers must be used in combination with a flat washer to be effective. Imported.