We made this for some good friends who own a mobile food cart, Superfresh Carts. The letters where made of 100% caps then filled with spray foam for support. We made each triangle individually then attached them to a strip of caps that served as the border. We ripped a piece of thin plywood to add rigidity to the border. The letters are attached to hardware cloth, which covers the entire area.
These are letters I made for Superfresh's new cart.