Select fine-grained, knot-free, soft wood, such as pine or cedar, in a standard 1 by 3 inch or 1 by 4 inch size. Cut two pieces 16 inches long and two pieces 22.5 inches long. Nail them together, as show in Fig. 10-1B, and add corner braces made by cutting a piece 2 by 2 inches diagonally.