How to Install a Support Post: Properly installed posts can mean the difference between a fence or trellis that leans after a season or two and one that lasts a decade or more. Here’s how to put them up right: 1) Dig a hole at least 24 inches deep and about three times the width of the post. If you live in an area where the soil freezes deeply in winter, be sure that the bottom of the post will be 12 inches or more below your frost line. For a heavy vine, dig a hole 24 to 36 inches deep. A post-hole digger makes the job easier. 2) Create a firm base. Put a large, flat stone at the bottom of the hole. For drainage, add gravel to the level of the top of the stone. Tamp the stone in place with post. 3) Set post. Set the post on top of the stone. Use a level to ensure that the post is vertically aligned inside the hole. Add another 2 to 3 inches of gravel to the hole. 4) Add concrete. In a wheelbarrow, combine ready-mix concrete with water until the mix is the consistency of peanut butter. Fill the hole with concrete—a few inches at a time—and tamp each layer to remove any air bubbles. Check to be sure the post is still plumb; realign if necessary. Mound concrete an inch or two above the ground, sloping it away from the post to allow water run-off. Cap each post for a fine finishing touch.