Dwarf French beans

You probably won't need support unless you are growing to get dried beans, particularly in a polytunnel as sheltered from any wind.

I generally end up putting stakes at the 4 corners and at intervals of about 6 to 8 feet along the row (if 20' row would have stake at each end and 2 spaced between, each side of row) then wrap twine round probably about 9" to a foot high and droop some of the leaves and pods over it. But I only need to do this when I grow for drying the beans.