The jaws move forward and downward as the ball screw is tightened. The jaws swivel 1.5 degrees from center to allow for clamping on uneven surfaces. Tightening the ball screw forces the clamp forward and downward against the workpiece supports and stops. Body made from 1045 alloy steel. Arm made from 1045 alloy steel and heat treated.Replaceable jaws are serrated for positive holding and made from M-2 high speed steel, hardened to Rc 60/62. Parts have black oxide finish.