A description referring now to fig1 4 a clamp 2 of one embodiment of the present invention is shown that includes an upper jaw 6 and a lower jaw 10 the upper jaw 6 is interconnected to a rack 14 the lower jaw 10 is connected to a carrier 18 that is operatively engaged to the rack 14 the carrier 18 also rotatably supports a crank 22 that includes a cog 26 selectively and operatively interconnected to the inside surface 30 of the rack the carrier 18 further employs a pawl 34 and that is operatively interconnected to an outside surface 38 of the rack 14 in some embodiments of the present invention the upper jaw 6 is rotatably interconnected to the rack 14 and the lower jaw 10 is rotatably interconnected to the carrier 18 which will be described in further detail below referring specifically now to fig3 the pawl 34 has an end 42 that selectively engages a space between adjacent teeth 46 of the outer surface 38 of the rack 14 the teeth 46 are shaped to allow movement of the pawl 34 in one direction and to prevent movement of the pawl 34 in an opposite direction thus the interaction of the pawl 34 and the teeth 46 maintain the distance between the upper jaw 6 and the lower jaw 10 such that the carrier 18 cannot be moved along direction a when the pawl 34 is engaged however pressure from below the carrier 18 or below the lower jaw 10 along direction b will move the lower jaw 10 towards the upper jaw 6 the pawl 34 is biased by a spring 50 wherein pressure along direction b will selectively move the.