Jacks are the foundation of any set. Well made jacks can last a very long time. Below is a relatively small Jack, but I have found that jacks that are in the 48 to 60 range can handle very much of the load required by 8 foot flats. Jacks with smaller footprints like this one are very important when standing flats back to back on a rolling dolly.
Below is a picture of my small jack that I used to stand fence pieces in our latest Community Theatre production of “Fiddle on the Roof”. They’re only two feet tall. The one next to it is a jack I built from re purposed fencing when I was desperate for wood, and they have lasted for approximately three years now.
My biggest jack is 7.5 feet tall and is mainly used to stand my larger proscenium pieces. With stabilizing braces on the proscenium flats, a pair of these jacks, and a small stabilizing arm toward the top is all that that I use to stage pieces up to 16 feet tall.