Set two 14-inch boards on edge, parallel and 34 inches apart. Set two 34-inch boards between them at right angles and spaced 10 inches apart. Screw through the 14-inch boards to the 34-inch boards using 3 screws for each corner. Set the 10-inch board between the 34-inch boards at a right angle so it is 16½ inches away from each 14-inch board. Screw through the 34-inch boards and into the 10-inch board using six screws. This is the top to your locker.
Position two 40-inch boards on edge, parallel and 34 inches apart. Set two 34-inch boards between them at right angles so they're spaced 38 inches apart. Screw this set of boards together following the same procedure that you did in the first step using 12 screws total. Set the 38-inch board on edge and between the 34-inch boards at a right angle so it is 16½ inches away from the 40-inch boards. Screw the 34-inch boards to the 38-inch boards using 6 screws. This is the bottom to your locker.
Lay the 16-by-34-inch plywood on top of the top locker frame so the edges are flush. Screw the plywood to the frame using 12 screws. This is the back to your locker and will give it stability. Lay the 40-inch plywood on top of the lower frame so the edges are flush and screw it to the pine boards using 20 screws. This is also the back to your locker frame.
Set the top of locker on the bottom section. Screw a coat hook to the plywood inside each lower locker space so it is 8 inches away from the vertical boards and 3 inches below the top horizontal 34-inch board.