Fender washers have a larger outside diameter than regular flat washers.
These washers are used to prevent pull-though and provide a greater bearing surface under the fastener.
This prevents nuts, bolts or screws from pulling through base material.
Fender Washers are distinguished from standard flat washers by their significantly larger outside Diameter (or OD), which creates a larger surface area on the fastener assembly, allowing it to withstand more force.
Fender Washers are commonly used to distribute load force on sheet metal, and gain their name from the use on car fenders.