Horizontal Clamp. Round Knurled boot fits typical Weldsale 1-3/4″ square hole. Clamping HEIGHT of 2 inch (with sliding arm reversed) to 15 inch. Throw of screw: 3-1/2 inch. Simply drop this clamp into a square hole, and it is ready to go. Clamp WILL tilt back as it makes contact with work piece. Clamping in all radial directions. Very simple and very fast clamping (and unclamping).