External Toothed Lock Washer, Hillman, Zinc-Plated

Internal toothed lock washers are hardened, circular washers with twisted prongs or teeth, extending inward from the inside edge. These teeth are used to prevent nuts and bolts from loosening caused by vibration and/or corrosion. External toothed lock washers have serrations around the outer diameter which provide better holding power due to a greater surface area.