I often recommend using a steel t-post to both train young trees and to help reduce buck rub. However, using steel fence posts have a down side. Once the tree grows above the top of the post the sharp edges of the post can cut into the bark of your tree creating a huge wound (photo at right). The wound is cut into the tree by the action of the wind moving the tree's trunk back and forth against the post.
There is an easy fix to prevent t-post rub. Cut the neck off a plastic drink bottle then place the bottle upside down over the post. The rounded, smooth bottomed bottle will guard the tree from the sharp, top edges of the t-post.