Square Washer

A square washer is a flat plate with a central hole, square in outline. It spreads load over a wider area than a round washer and resists turning in square or slotted holes.

A square washer spreads a load over a flat area and gives a square bearing face where a round washer would turn. It often sits under a nut or bolt head on timber, steelwork or slotted holes. It matches the thread of the bolt or nut it serves and the hole or slot it covers.

This kind of part is often made in stainless steel 304. That material gives good corrosion resistance for general outdoor and indoor use. It is not intended for highly acidic or chloride-rich environments.

This is a general guide to checking this kind of part. It says nothing about any supplier's parts.

Ask for a certificate of conformance for the material and dimensions. On receipt, check the hole size, the squareness of the plate and the surface for cracks or burrs. Confirm the grade marking matches the paperwork.