Rubber WASHERS are disks of rubber placed beneath a nut, an axle bearing, or a joint, to relieve friction, prevents leakage, isolate, prevent loosening or distribute pressure. There are many different types of washers and washer-type products for a variety of applications. Common types include Flat Washers, C-Washers, D-shaped Washers, Sealing Washers, Spherical Washers, Square Washers & Shoulder Washers. Flat Washers are thin, flat, and circular general-purpose washers, with a centrally located hole.