Mason Flat Washer

A mason flat washer is a flat circular washer with a large outside diameter relative to its hole, used to spread load over a wider area. It is commonly placed under a nut or bolt head on softer materials.

A mason flat washer is used to spread load over a wider area than a standard flat washer. It often sits under a nut or bolt head on soft or irregular surfaces. It can be matched with a bolt or screw of the same thread and a nut where required.

Galvanised finish is a zinc coating that gives moderate corrosion protection for outdoor and damp indoor use. It is not a substitute for hot-dip galvanising in aggressive environments.

This washer is often made in galvanised carbon steel. It can also be made in stainless steel A2 or A4 for better corrosion resistance. Stainless steel A4 is often chosen for marine or chemical exposure.

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 covering material and finish. Check outside diameter, hole size, thickness and flatness on receipt, and confirm the coating is uniform with no bare patches.