Equine Leather Lead up or Short Tie Down by Western Rawhide Read more.
Tie downs are useful in postponing going from popping up the head to flipping over. They certainly do not relieve the frustration that cause the behavior. But when that critical moment occurs, there won't be much rearing.
While it's easy to assume a tie-down is used only to keep a horse's head down, the purpose of a properly adjusted tie-down is to provide your horse with a piece of equipment to brace on for balance.