Teeth on the outside edge bite into both the fastener and the mating surface for a stronger hold than internal-tooth lock washers. However, they may mar your material and snag on objects. Pair these washers with nuts and screws that are large enough to make contact with the teeth, such as pan, button, and binding head screws.

18-8 Stainless Steel—The choice for wet and outdoor environments, these washers won't rust when exposed to moisture. However, they can't hold up to the harsh chemicals that 316 stainless steel can.

Super-Corrosion-Resistant 316 Stainless Steel—Superior to 18-8 stainless steel, these washers won't degrade when exposed to harsh weather, salt water, and most chemicals.

Zinc-Plated Steel—A common choice for areas with occasional exposure to moisture.

Internal teeth dig into the nut or screw to prevent it from backing out. Unlike external-tooth lock washers, these have a smooth outside edge, so they are less likely to mar your material or snag on objects. However, they don’t grip quite as well. Pair them with fasteners that have small diameters, such as fillister and cheese head screws.

18-8 Stainless Steel—The choice for wet and outdoor environments, these washers won't rust when exposed to moisture. However, they can't hold up to the harsh chemicals that 316 stainless steel can.

Zinc-Plated Steel—A common choice for areas with occasional exposure to moisture.

Black-Oxide Steel—Typically chosen for their appearance, these washers have a dark, matte coating that creates a finished look. They offer minimal corrosion resistance, so they're best for dry environments.