GM-35016-B holds the pinion flange to allow removal and installation of the pinion flange nut.  GM-35016-B is mounted in a vise, and the pinion flange (still attached to the pinion assembly) is lined up with the holes in GM-35016-B, and then attached to GM-35016-B.  The pinion flange nut can then be accessed through GM-35016-B to remove and install the nut as directed by the service procedure.  GM-35016-B has multiple hole patterns to allow use on 292 mm and 320 mm rear axle pinion flange.