Fastener Symmetry

Nuts and washers might at first appear to be symmetrical, but upon closer inspection, a difference in "sides" can be determined. The nut or washer will have a flat side called the hard edge, and a rounded side called the crown edge. When installing the fasteners, the hard edge should be toward the mounting surface, and the crown edge away from the mounting surface. This is also true when combining a washer and nut together. The washer hard edge is against the mounting surface, the nut hard edge is contacting the washer crown edge.