I used an articulated ladder similar to this product at Lowe. There are
4 sections, each 4'4" long. By using the end sections as legs I had a
platform 4' high and 8 feet long. I put a piece of plywood cut to fit
over the top section. If the link doesn't work search Lowes.com for
"ladder" Price was $150.
http://www.lowes.com/lkn?action=productDetail&productId=161406-000000287-M1-8-16