If mail box holders had to be insured, the rates would be high, since they are stoned by children, hit by cars and snowed under, at the very least, by snowplows.
Here’s one that could apply for lower insurance rates. It’s set up at an angle that lets it reach out toward the highway. It is swiveled in the center, so it will give a little when hit. And, at 3′8″ above the surface of the highway, it’s at a comfortable level for that mailman stretching out of his car.
Note carefully that two arms reach out from the post, and that the base for the mail box is formed by those two arms plus a block of 2×4 between them. Weyerhaueser recommends nailing arms as well as gluing them to the upright. Countersunk wood screws would do equally well.
