Save time by assembling screws and washers in advance. The tabs on these washers grip the screw shank, so they won't slip off, even when fastening upside down or at odd angles. They take the pressure off screws and nuts to protect mounting surfaces.

Nylon—The most popular plastic washers, these are strong, durable, and economical. Nylon will swell and weaken when exposed to moisture, so these washers are best for dry environments.

The wavy shape flexes like a spring to keep nuts and screws secure on slightly uneven surfaces. These washers add a small amount of tension to stop fasteners from backing out due to mild vibration. While they don't hold as well as other lock washers, they do grip slightly better than curved washers. They work best in electrical panels, light fixtures, and other light duty assemblies. Since these washers hold their shape when untightened, you can reuse them a handful of times without losing strength.

Steel—Best for dry environments since moisture will cause these washers to rust.

3 Wave—More points of contact than single-wave washers for a better grip.