Adjustment at the touch of a button directly on the work piece. Fine adjustment for optimum adaptation to different size work pieces and a comfortable gripping position. Self-locking on pipes and nuts: no slipping on the work piece and low hand force required. Gripping surfaces with special hardened teeth, teeth hardness approx. 61 HRC: low wear and reliable gripping. Box-joint design: high stability because of double guide. Reliable catching of the hinge bolt: no unintentional shifting. Pinch guard prevents operators fingers being pinched. Chrome vanadium electric steel, forged, oil-hardened.