This is a specialized thick, short, stocky wrench with a block end to the handle specifically designed for use with a hammer, enabling one to impart great force. Used commonly with large fasteners, especially a nut and stud which both have index marks, the nut is screwed hand-tight, then further tightened with the striking wrench a known number of index marks calculated from the elasticity of the bolt or stud, thus giving precise torque (preload).