Stud chains can be a great tool on horses when used correctly. before ever using a stud chain on your horse, ask a professional for a lesson on the purpose of horse stud chains and correct methods of use. Stud chains are an easy aid to misuse, but used correctly are much more human than other methods of horse control. Stud chains are not just for stallions- any horse while exhibits unsafe behavior while being led or handled may benefit from the use of a stud chain.
Horse stud chains should be put on OVER the nose unless showing in western halter classes. For general handling and stud chain effectiveness, a stud chain should cross over the nose, through the ring on the halter on the opposite side, then be crossed under the jaw and clipped to the O ring on the near side of the halter, just below the buckle. This method of attachment maximizes control, ensures the halter isn't pulled askew by the chain, and minimizes the possibility of unintentional misuse. Never attach a stud chain under the jaw of a misbehaving horse. A stud chain attached in this way may encourage a horse to toss their head or rear.
S tud chain should never be held tautly. Your lead shank, attached to the chain, should be "popped", just like a choke chain on a dog, it hurts the horse and just numbs them to keep it taunt the entire time it is on. If introduced correctly, you should never have to be aggressive with a stud chain. Once a horse knows what a stud chain is and what it is for, a stud chain is mostly a psychological tool- when the horse feels the weight of the chain on their nose, they know there will be consequences for misbehaving, so they won't even try.
There is a myth that claims a misused stud chain can break a horse's nose. The truth is, there is no way a human body has the force to can break the nose of even a small horse with a stud chain. Tying a horse by a stud chain, however, is extremely dangerous and should never be done under any circumstance. It is also worth noting that a stud chain should not and cannot be put on for the first time during a time when the horse is acting up or especially not when the horse is scared. Like any training aid, the aid should be introduced gently when the horse is in a relaxed, teachable state. A stud chain should be used for managing a horse in a difficult situation only after the horse has learned in a relaxed state what the stud chain is and how it works and what behavior releases the correction.
An appropriately used stud chain is an excellent tool. An inappropriately used chain is extremely dangerous to horse and handler. We highly recommend getting a short lesson in appropriate use from a trainer you trust before ever attempting to use a stud chain.