These Forgefix Square Plate Washers have a larger surface area than most round washers, making them suitable for heavy-duty fastening. They are ideal to be used with Carriage Bolts in structural timber fastening applications such as joist work & decking. The washers are bright Zinc Plated for increased resistance to corrosion. APPLICATION: Many structural applications where timber to timber fastening are required. The large surface area distributes the load evenly under the bolt head. Can be used with all types of bolts & nuts. Zinc coatings prevent oxidation of the protected metal to create a longer lasting finish. It does this by forming a barrier & by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not trigger a breakdown of the substrate&8217;s surface integrity as it is formed. The zinc oxide, if left intact, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminum & stainless steels by their oxide layers. Square Plate Washer ZP 50 x 50 x 10mm Box