My hobby machine shop is very small so space is a premium. I had a built-in bench but I took it out to gain space. I decided to build a sturdy portable bench that I could roll out of the way when it was not in use. I wanted my vise attached to it so in order to gain stability it had to be heavy, very heavy.
It is 22" by 32" and supported by three wheels (Surplus Center) each rated at 1000 pounds. The single wheel at the vice end is an articulation (up or down) swivel type caster made with ball bearings from a crank on a bicycle. The two shelves are made using 3.5 inches of concrete. The total weight is approximately 600 pounds. It is very stable when the caster is lifted and the weight falls on the vise support post (rubber pad on the bottom). I put 1/8 in masonite on top of the two shelves. I am very pleased with the results.