You don't want you precious RepRap Darwin to do destructive work, such as ruining the lacquer of your desktop. Instead it should be a purely constructive machine!
Warning: with these feet, your machine may still walk around over your table top (no anti slipping included), but with style, of course. You might want to add rubber soles for extra anti slipping.
N.B. I'm merely uploading it, design and photo by Tony (tofletcher).
You might need some spacers and slightly longer metal rods (as seen in the photo).