Set the dado blade to cut a groove 1 / 4 inches wide. Adjust the depth of the blades 1 / 4 inch well.

Adjust the guide table saw so you have 5 inches between the blade and the fence. Adjust the fence so it won 't move. Place one of the pieces one-by-12-by-26-inch lumber on the saw table so that the widest side of it is flat on the table. Put the saw.

Place the edge 11 1/2-inch wood against the fence and run it on the blade. Turn the timber over and restart. Turn the timber around so the opposite edge 11 is 1/2-inch against the fence. Run the wood on the blade, turn it over and run it again.

Repeat with the other three parts 1-by-12-by-26-inch lumber. Run the last two pieces on one side 1/2-inch 11. Put the saw.

Move the guide of the table saw blade gap until you have 10 1/4-inch between the fence and the blade. Adjust the fence so it won 't move. Run the wood that you did before. Remember to run the last two on one side.

Put the two pieces of 1-by-12-by-29 1/2-inch pieces of wood on the table. Measuring a 1/2-inch rim 11 and make marks at 3 / 4, 5 3 / 4, 6 1 / 2, 11 1 / 2, 12 1 / 4, 17 1 / 4, 18, 23, 23 3 / 4 and 28 3 / 4 inches. Place the framing square marks and draw lines through the woods.

Drill three holes between the lines with the 1/16-inch drill bit. Place a 1 inch from each edge of the timber and the middle third between the two. Turn both pieces over and drill countersink holes in the same place that the holes 3 / 8 inch deep.

Secure partitions between the 1-by-12-by-29 1/2-inch pieces of wood between the lines and sides with drywall screws. Then attach the piece of plywood 29 1/2-by-27 1/2-by-1/4-inch on the mail box sorter box with nails. Be sure to attach the walls and the top, bottom and sides.

Turn the box and insert the plywood 5 1/2-by-11 1/2-by-1/4-inch in the grooves. Sand the edges with 100 grit sandpaper, if too tight.