Gather your supplies
• Post1–200x50 x 1400mm treated pine sleeper
• Post2–200x50 x 1400mm treated pine sleeper
• Post3–200x50 x 1100mm treated pine sleeper
• Post4–200x50 x 1350mm treated pine sleeper
• Post5–200x50 x 850mm treated pine sleeper
• Bottom brace 200 x 50 x 1300mm treated pine sleeper
• Front 200 x 50 x 600mm treated pine sleeper
• Top and bottom (4) 200 x 50 x 700mm treated pine sleeper
• Sides (2) 200 x 50 x 400mm treated pine sleeper
• Back (2) 200 x 50 x 200mm treated pine sleeper
• Door 200 x 50 x 300mm treated pine sleeper
• Long door track (2) 19 x 19 x 600mm hardwood stake
• Short door track (2) 19 x 19 x 200mm hardwood stake
• Support blocks (2) 50 x 50 x 200mm treated pine sleeper
You’ll also need
Power saw; electric plane; jigsaw; router with 10mm straight-cut bit; 100mm bugle-head screws; rapid-set concrete; exterior acrylic gap filler; outdoor paint in chosen colours (we used Dulux Weathershield Low Sheen in Bogart; Dulux Weathershield Gloss Acrylic in Energos)
Clear out area for your letterbox. Dig a 400mm wide by 300mm deep trench 1.5m long. Take care if there are any underground services.
Cut all timber to length (see box, left). Use electric plane to smooth off front of posts that will be above ground.
Print numbers from computer and trace them on top of post number 4. Use a spade bit that is slightly narrower than numbers to remove bulk of timber. For best finish, drill so point of spade bit just pokes through timber. Turn it over and drill back other way using hole as a guide. Jigsaw out sides of numbers and sand edges smooth.
Lay posts out on bench with bottoms lined up and 100mm spacing blocks between them. For line pattern on the face, draw random parallel lines 32mm apart, across posts until you are happy with the design.
Remove spacing blocks and butt posts together so 1 set of lines meets across posts. Nail 2 straightedges across posts as a guide for base plate of router, ensuring router bit is on cutting line. Set router at a depth of 5mm. Start so cutting edge of router bit is rotating into timber. Make several passes along work, changing depth for each pass until you have a groove 10mm deep. Reposition posts and straightedges to rout other grooves. Sand edges smooth.
Reset posts so they are lined up with spacing blocks in place. Cut 200mm off both posts 1 and 2 to hold letterbox. Set short pieces aside. Put bottom brace along posts so top of brace will be at ground level and screw into each post. Nail a temporary brace along top of posts to hold them in position.
Put posts in trench, check for plumb and brace. Fill with concrete so it’s below the soil, then soak.
On front panel of letterbox, draw a slot 28mm wide and 300mm long, centred on face. Drill out ends with a 28mm spade bit. Using jigsaw, join holes to make mail slot. Put top pieces on bench, with sides and front sitting on edge. Front piece is recessed 10mm from face of letterbox. Finish by putting on bottom pieces and screwing them to sides and front, which should also be screwed together. Do not screw top pieces on at this stage.
Turn mailbox over and place back pieces on inside of box 70mm from rear. Screw through side and bottom of back pieces. Screw long door track onto bottom of box flush with rear, and short door track between back pieces flush with rear of back pieces. Drill a 28mm hole through door and put in position.
Screw support blocks into top of first 2 posts. Place letterbox on top so it overhangs uprights by 150mm at front and 100mm on each side. Screw down through bottom into support blocks and uprights.
Screw short parts of first 2 posts you cut earlier to back edge of front top piece to match their positions below box. Fix door tracks to other top piece to match their positions on bottom, so routed lines are aligned. Screw them to box.
Seal gap between top pieces using filler. Apply 2 coats of outdoor paint. Highlight routed grooves and inside of numbers with a contrasting colour for visibility.