The Grub Screw is a threaded screw that secures the front trailing arm to the torsion leaves. If they are loose, the front end can fall apart.
Make sure yours are tightened properly and in good shape.
Fits all years of Standard Beetle, Karmann Ghia and Thing.
6 required per car. 1 at each trailing arm and another in the center of each tube of the axle beam, holding the leaf springs side to side.