Draw two triangles on the 12-inch plywood. Each triangle must have a 6-inch base, two 45-degree angles at the base and a 90-degree angle at the apex. Use the 6-inch edges for the bases of the triangles. Cut out the triangles using your table saw.
Draw a line down the center of each triangle starting at the apex. These lines are at a 45-degree angle to each edge. Drill a 1-inch hole 2 ½ inches below the apexes along these lines.
Cut the ends of each 48-inch board and 69-inch board at a 45-degree angle using your miter saw. When the boards are set on edge they should resemble a trapezoid shape.
Lay two 48-inch boards flat and at a 90-degree angle. The cut edges should be against each other and the corner should be flush. Lay one of the plywood triangles on top of the boards so the 90-degree corners are flush. Screw the plywood to the boards using four screws. Lay a 69-inch board on top of the 48-inch boards so the angled ends are flush with the edges of the boards. Screw the 69-inch board to the 48-inch board using four screws. Repeat this step. These are the two sides to your cable spool rack.
Position the sides upright so they're resting on the edge of the 69-inch boards. The 48-inch boards should be between the 69-inch boards and the plywood. Space the sides so the outside edges of the 48-inch boards are 60 inches apart. Position the 60-inch boards perpendicularly against the rack so there is one on the front and one on the back. Their ends should be flush with the sides of the 48-inch boards and they should be 20 inches below the plywood triangles on either side. Screw them to the 48-inch boards using four screws for each board.
Insert the pipe through the holes in the plywood and through the cable spools. Tighten the end-caps around the pipe ends to secure them.