Forgefix square plate washer zp forgefix 10sqpl5016 these forgefix square plate washers have a larger surface area than most round washers making them suitable for heavy duty fastening they are ideal for use with carriage bolts in structural timber fastening applications such as joist work and decking the washers are bright zinc plated for increased resistance to corrosion many structural applications where timber to timber fastening is required the large surface area distributes the loa