Recently reset my body on frame and many of the original body washers were cupped. Over half of them were cupped, some very visibly cupped and others only barely cupped. Most were very thick like nothing I could find in hardware stores. A few were thinner than all the others and of one or two of those, the cupping was not uniform across the washer, as if due to an off-center nut/bolt combined with over tightening.
I sanded them all by hand then primed and painted each one. After that I stared at them and handled them for months like stress-reducing rubbing stones until I had several sets of four that were similar in flatness, or cupping, or non-uniformity and a few pairs that were similar. I enjoyed that each washer was slightly different than the next.
While grouping the washers in four's and two's I noticed that the outer edge of each washer had a sharp edge and a curved edge. Almost all my washers were cupped on the side with the sharp edge except one or two. I assumed the cupped, sharp edge sides faced the nut on the underside of the body and faced the bolt head for the two toe-board washers inside the body and the four washers inside the trunk.
