IRWIN Vise-Grip locking wrench locks on to nuts, bolts and other hex fasteners on three sides unlike conventional wrenches that grip on to only two sides. This prevents the jaws from slipping, which prevents rounding and marring of the fastener. Have a self-energising lower jaw that allows for 3X more gripping power and have a 2X longer life as the high grade alloy steel is heat treated for maxium durabilty. Hex key adjusting screw that tightens to draw materials closer together and also provides controlled release.