My team used a forklift in 2005. We made it out of 1in x 1in 80/20 Aluminum. We used delrin slides to connect them, and pulleys and wires to lift it. It worked fast but (if you use a wire) you must keep the wire taunt, and you want to power it up and down. I forget where we purchased the materials from.
here is a link to our 2005 gallery