Set the three boards on edge, parallel and 9 1/2 inches apart. Lay the plywood on top of the boards so the sides and ends of the boards are flush with the edges of the plywood. Drill twelve 3/32-inch pilot holes through the plywood so four holes enter the edge of each board. Space the holes 6 inches apart and be sure they enter the center of the edge of each board. Screw the boards together with the pilot holes as a guide.
Sand the display rack. Wipe it clean and apply the wood stain. Let the stain dry.
Locate studs in the wall using your stud finder. Position the rack on the wall with the plywood against the wall. Use the level to make sure the boards are horizontal. Attach the rack to the wall with the 4-inch screws, two for each stud.