David, What I usually do is cut short pieces of wood 2x4 to fit in between the metal stubs right at the floor level and anchor them to the bottom track with a couple of the same screws you use to assemble the metal studs. You can lay them flat right in the bottom track or stand them on edge and screw them in that way, which I sometimes do with wide baseboard. It is a little more work to use the wood, but the holding power of the wood will be better, especially in some basements where the moisture level varies. I have tried different ways, and prefer this to others. Works especially well if you are going to use an air nailer to install the baseboards.