Mine is a wooden buck type that I made with leftover wood from a deck project. They need to be a minimum of two feet off the ground to save your back. I don't like bending over or having to squat down. Have repaired both knees, and don't want that again. The wooden ones present problems for getting them up on to it. My car was a roller and pretty heavy. Since I didn't know where the COG was, and there wasn't a foll bar for lifting, I had to hoist up one end, slide one end under, strap the straight rails to the frame, lift the other end and secure with carrige bolts on shouldered uprights(notch the 6x6 uprights for the rails to sit on). Then have dolly wheels on one end and a pry lift on the other for the hand truck. Easily moved around on the work floor. Great for a build. My build area was 2 garage type, but one in front of the other. So when there was maintenance on one of the family vehicles, the project had to move forward. Just remember that the thing has to be braced with either plywoood panels in the front and rear or sturdy X bracing all around. When you are pushing or pulling something, you don't want it to come crashing down.
Bill