These hook clamps are designed to move up and down in conjunction with the tightening screw. They are actuated in both directions with the hex screw on top of the clamp to prevent galling of the workpiece. The holder provides additional clamping height. Hook clamps are commonly used to hold down fixture and workpieces on a wide variety of machines. The clamp arm can be swiveled out of the way for easy part insertion and removal. The clamp body is made from 4140 alloy steel, quenched and tempered, with a black oxide finish. The holder is made from 1045 steel, quenched and tempered, with a black oxide finish.