What type of washer is designed with teeth to prevent slipping?

The type of washer designed with teeth to prevent slipping is referred to as shake-proof washers. These washers feature a serrated or toothed surface that grips the material to which they are fastened, creating friction that helps to keep the bolt or nut secure. This gripping action is particularly useful in applications where vibrations or movement may loosen standard fasteners over time.

While other types of washers serve different purposes—such as flat washers, which distribute load or provide a smooth surface; split washers, which are designed to expand when compressed and relieve pressure; and lock washers, which can have various designs including split or toothed types that also aim to prevent loosening—the defining characteristic of shake-proof washers is their specific tooth design that locks them in place, effectively reducing the chance of slippage.