An adjustable clamp for the retention of a vice or work piece onto a slotted worktable. The clamp has a raised rear foot that both spans the standard width of a slot in a slotted worktable regardless of the angle the clamp is secured to the worktable, and generates an increased gripping force at both contact points of the clamp. Its nose accommodates a cylindrical pin recess to accommodate a cylindrical pin to allow the vice to clamp to a vice with a raised peripheral lip. The 30 degree beveled front edge allows the clamp a substantial planar contact surface with the vice or work piece, enhancing stability.