This is a clip that attaches to the top of your orbital sander. It is so that when you are sanding top-down, for example, sanding an old door on some saw horses, or a small part of a wooden floor, that you can add the balanced weight of dumbbells to the top of your orbital sander. The extra weight = less effort to smooth the wood, and the peripheral distribution of the weight= stability when sanding.
-- leinypoo13, Nov 30 2008

random, halfbakery