Hand Knob Swivel Screw Clamp With Small Pad – 1/2-13 Thread X 3-15/16. Use When Hand Tightening Is Necessary. Pad Can Pass Through Tapped Hole. Pad Swivels In All Direction, And Makes Maximum Contact With Angled Of Uneven Surfaces. When Pad Comes Into Contact With Part Or Workpiece, It Stops Rotating And Thus Prevents Marring. Black Oxide Finish On Stem. Aluminum Handle.