I prefer threaded fasteners for adjusting the base of anything to the floor. More likely to remain where i put them and not work their way out.
I really prefer the tri-pod approach as above, but it just doesn't work for all things.
I'm making a "vise-topper" as seen this thread presently. I'm letting in the bottom piece just a bit. Then i have to remove the brake drum. It's standing-height only now, and that's not good for my feet. I'll bring in a wide base or bolt it through the floor. Yeah, bolt it through. My house, my hardwood!