Spread wood glue on the joints, then nail them together with 8d nails.
Build this handy stool in one hour and park it in your closet. You can also use it as a step to reach the high shelf. To make the storage shelves, all you need is a 4 ft. x 4 ft. sheet of 3/4-in. plywood, wood glue and a handful of 8d finish nails. Cut the plywood pieces according to the illustration. Spread wood glue on the joints, then nail them together with 8d nails. First, nail through the sides into the back. Then nail through the top into the sides and back. Finally, mark the location of the two shelves and nail through the sides into the shelves.