Strongbacks are metal beams that help to support walls or structures. They can be used in various ways. They can spread the pressure of props against them. And they can go either side of shuttering, with steel rods through the shutters, to tie them together, which forms the mould to pour concrete in.
Below, wooden shuttering has had concrete poured inside. The strongbacks on either side provided extra strength to prevent the shuttering from blowing.
