michael_x:
You want a third hand, not a bench vice ( vise ? ).
A hand is movable, by definitionshould just have a stable base to not move too easily or by itself...
I'd rather prefer a heavy solid base, which discourages any attempt to drill mounting holes.
Perhaps I was unclear. I wanted drill holes so that I could put a larger base in so that the third hand wouldn't tip, particularly if you use the soldering stand that comes with the cheap kits. If the units came with a proper base that is at least 6"/17cm wide in each direction (or one that is heavy enough) then I wouldn't need drill holes. All of the third hand units I've seen in person or on the net, have tiny/flimsy bases.
In fact, I was soldering tonight with my third hand unit, and it was unstable, particularly when I put the soldering iron in the holder.
A second thing that was in my mind, but I didn't mention, was to put wood or plastic underneath so that when my daughter solders, she doesn't scratch the table she is using.