Self-clinching nuts are installed by placing them in properly sized holes in sheets and applying a parallel squeezing force to the head of the nut. The sheet metal surrounding the head cold flows into an undercut thereby making the fastener an integral part of the sheet. A serrated clinching ring prevents the fastener from rotating after installation. Provide load-bearing threads in thin sheets with high pushout and torque-out resistance. Types S / SS are recommended for use in steel or aluminum sheets HRB (Rockwell "B" scale) 80 or less and HB (Hardness Brinell) 150 or less.