Cut one piece of pressure-treated four-by-four lumber to a length of 78 inches to serve as the vertical stand. Cut a pressure-treated four-by-four crosspiece to a length of 36 inches. Measure distances of 56 1/2 inches and 60 inches from the bottom of the vertical member. Measure distances of 18 and 21 1/2 inches from one end of the crosspiece. Mark these distances by drawing a straight line across one face of each board at each distance.
Install a stacked dado blade in your table saw. Raise the blade height to one and 3/4 inches from the cutting surface. Insert the miter gauge in one of the grooves on the surface of the saw. Set the miter gauge to zero degrees. Hold the vertical board tight against the flat front surface of the miter gauge and align the outside edge of the dado with your first guideline. Turn on the saw and carefully push the board through the saw blade. Repeat this process until you have removed from the face of the board an area of one and three quarters inches by three and one half inches by three and one half inches. Repeat the process with the crosspiece to remove the area between the 18-inch and 21 1/2-inch marks.
Glue the cut-out surface on the face of the vertical piece. Insert the crosspiece into the cut-out, so that the cut-out surface of each board meets, and the two interlock to form an off-center "T" with a consistently even face on both sides. Pre-drill three half-inch holes in a triangle pattern where the two boards are locked together. Carefully turn the assembly over and counter-sink a 3/4-inch area at the opposite end of each hole to create space for a nut to be inserted.
Turn the assembly over once more, and push one half-inch by three and one half-inch carriage bolt through each pre-drilled hole. Protect the surface of the wood by putting each bolt through a washer before inserting it in the hole. Turn the mailbox post over and thread a nut onto the end of each bolt. Use a socket wrench to tighten each nut until you can no longer tighten it.
Dig a hole that is one foot wide and 18 inches deep using a posthole digger. Insert the mailbox post into the center of the hole, with the long arm of the crosspiece pointed toward the street. Use a spirit level to keep the post perfectly vertical while an assistant pours quick-setting concrete into the hole. Place two-by-fours at 45-degree angles around the post to hold it vertical while the concrete sets. This should happen between 20 and 40 minutes after you pour it, depending on the circumstances. After the concrete sets, shovel dirt over the top of it.
Things You Will Need
- Four-by-four treated lumber
- Table saw
- Stacked dado blade
- Tape measure
- 1/2-inch carriage bolts, 3 1/2 inches long
- 1/2-inch drill bit
- Electric drill
- Socket wrench
- Post hole digger
- Quick-setting concrete
- Scrap two-by-four lumber
- You can give your mailbox post extra appeal by building it out of stone instead of wood, or adding paneling and decoration to the wooden four-by-four frame.