? Can be used on base, end, and flat on either side as clamp is within outside width of block. Clamp is provided with an adjustable side screw with caps to support block and prevent tilting. Groove at stepped end at right angle to base and is handy for holding shouldered studs, round pins, etc. Hole clearance for drilling and remove dowel pins provided. Block has four 3/8?16 tapped holes, two in base and one on each side to attach angle iron. Angle iron holding block can then be attached to lathe face-plate or held by magnetic chuck. Block made of hardened steel. Sides are ground parallel and the groove central and parallel to sides and base. Size 1?7/8 inches square, base length about 3?1/2 inches.