The hanger holds the target to the side of the post so those occasional misses are much less likely to damage your post than hanging a target directly in front of the post. Provide your own belting (rubber belting usually lasts the longest) or chain to hang a target off a standard T post.
 
Metal hanger bracket only
Easily slides on and off the post but stays put when shot
Great hanging solution when your shooting pasture is shared with livestock.