- 1). Determine the location of the mailbox posthole from the guidelines above or after consulting local regulations. Use the tape measure and place it on one end of the post. Run the tape down the length of the post and make a mark, with the pencil, between 41 inches and 45 inches.
- 2). Run the tape from the other end of the post to determine the depth of the posthole. The measurement will be between 27 inches and 31 inches.
- 3). Dig the hole using the posthole diggers. Set the removed dirt to one side of the hole. Use the tape measure to check the depth of the hole as you proceed.
- 4). Insert the post into the hole once the desired depth has been reached. Backfill some of the dirt, approximately six inches to eight inches, around the post to hold it upright. Use the blunt end of the rock bar to tamp the soil in place. Use the level to align the post vertically on two sides, 90 degrees apart, of the post.
- 5). Mix the concrete according to the manufacturer's instructions. The addition of the concrete is optional and not required by USPS standards. If you are not using concrete, add soil six inches to eight inches at a time and tamp firm with the rock bar. Continue until the hole is filled. Check the vertical level of the post often with the level.