Mark the position on the ground for each post and begin digging the holes

After you lay out your new facility on the ground, mark the position on the ground for each post and begin digging the holes. Center the posthole digger over the nail with the colored flagging attached to it. Dig the holes 30 inches (76cm) deep in 10-to12 inch (25 to 30cm) diameter holes and set the posts in concrete. Pour concrete in the hole then lift the post so there are 6 inches (15cm) of concrete below the bottom of the post.