This box is 3 boards high (cedar dog-eared fence pickets), using the full length of the pickets for the sides and 1/2 the length of the boards for the ends. The dog ears were removed with a pull saw before painting and construction.
A 12ft, 8 inch wide, pressure treated pine plank was used to create a bench shelf along the sides. The plank was halved to create 2 benches. Small, 1 x 2s hold all three boards flush to form the sides. Segments of 2 x 4's were secured to create braces that hold the benches. The upper level of the end boards are longer than the bottom two and serve as additional support for the ends of the pine bench boards.
Wood screws were used for assembly. Corner brackets reinforce the interior corners for added stability. All exterior boards were painted before assembly.
The bed interior is 17" deep 33" wide x 71" long.