Abstract: The clamp comprises an L-shaped fixed member and an L-shaped sliding member retained by a loop thereon to be slidable along the post portion of the fixed member. A clamping screw threadably engages the slide bar portion of the sliding member above the loop, and bears against the inner surface of the post.When the sliding member first engages a workpiece it tilts only slightly, and in an anticlockwise direction as illustrated in FIG. 1. Upon tightening of the clamping screw, the sliding member is tilted slightly but in a clockwise direction, correcting the initial tilt and maintaining the jaws substantially parallel.Since the clamping screw bears against the post with a greater pressure than the pressure applied to the workpiece, the clamp does not rely upon tilting to grip the post.