I have been working with horses my whole life, and it surprises me the number of people (even some professional people) who were never taught the proper way to handle a horse when someone else is working on them. I was lucky. When I was 19, I went to work for an equine vet who had grown up on a working cattle ranch. Jesse was awesome with horses. What he taught me about handling even the most difficult horses has been a huge help for my entire career. And I thought that the basics of what he taught me might be helpful to the readers of Of Horse.
The first thing you need to keep in mind is that you are there for safety reasons. Vets and shoers are often in precarious positions while they do their job. It is very easy for them to get kicked, knocked down, or trampled. And it's your job to make sure that doesn't happen. If the horse is tranquilized, this is even more important to remember. A heavily sedated horse can still be startled suddenly, and may react much more violently than he normally would. I have been injured twice while handling a horse on the ground, and both times the horse was heavily tranquilized. So never take a tranquilized horse for granted.
The proper way to hold a horse is the same whether you're holding him for the vet, the shoer, your trainer or coach, or even your friend down the street, so for simplicity's sake I will only be using the term vet or shoer in my descriptions.
The safest place to be around a horse is by his shoulder. It would be extremely difficult for him to kick, bite, or strike you as long as you stay by his shoulder. This is also the best position to keep control of him, because it gives you good leverage on his head if you need it. So, if the vet is working on the horse anywhere behind the shoulder, stand by the shoulder, on the same side as the vet, facing him. Hold the horse near his halter with the hand nearest him, with the slack of the lead in the other. You should hold close to the horse's head, and keep a very light contact with him. Make sure your hand is relaxed. If you tighten or tense up, the horse will tense up in response. If you leave too much slack in the lead and the horse becomes upset or agitated, he can quickly get in a position to kick you or the vet before you can get control of him. If your horse is pretty relaxed your job is just to keep him still. If he moves forward or back, cue him as you would in normal circumstances. If he moves away from the vet, push his head away from you with the hand holding him, while bracing his shoulder with the other hand. This move is a little tricky and may require a little practice on your own to get the hang of it. But basically if you push his head one way, it will force his butt in the opposite direction. Try it when it's just you and your horse to see how it works. You just want to be sure and not over-do it and push him into the vet.
If your horse becomes agitated and very tense, you may have to let him move forward. In this case, you want to pull his head toward you, and allow him to make a circle around you if necessary. By pulling his head toward you, you turn his butt away from the vet, making it less likely that he will get kicked. If you need to circle your horse, ideally the vet should be in the center of the circle, with you making a small circle and the horse a larger circle around the vet.
Sometimes if your horse gets agitated, he will run backward. DO NOT PULL ON HIM. Pulling on him is the worst thing you can do. Walk back with him as calmly as possible, keeping a light, steady pressure on the lead until he calms down. Pulling on him will make him run back harder and faster and may result in him panicking and rearing and/or falling over backward.
If the vet is working on your horse's shoulder or neck, you need to stand far enough forward to be out of the vet's way. But you still want to stay on the same side as the vet. DO NOT STAND DIRECTLY IN FRONT OF THE HORSE. If you stand on the same side as the vet, and the horse panics, he will go around you, and you can safely circle him. If you stand directly in front of him, there's no telling which way he'll go, including right over the top of you. So always stand to the side.
If the vet has to work on your horse's head or face, or when your shoer has your horse's foreleg pulled forward to finish off, you will have to stand on the opposite side. For the shoer, stand off to the opposite side, facing your shoer. You may have to keep the horse's head slightly toward you in order to give your shoer room. With the vet working on your horse's head, you may need to keep his head still. Stand facing the back of the horse, on the opposite side from the vet and hold the horse's halter lightly with both hands, one on each side. Again, the main thing is to keep a light, relaxed hold. If you're tense or tight, your horse will be also.
Just a couple of other tips: If your shoer has a back leg up, and your horse tries to move forward, use as little pressure as possible to keep him from going forward. If you use too much pressure, it will cause him to put his weight on his hind end and on the shoer and may result in him jerking his foot away or even jerking the shoer down. So be careful of your pressure here. Also, if your vet is working on your horse's back end or leg (unless the leg is picked up), you can pick up your horse's front leg on the same side. This makes it much more difficult for him to wiggle around and almost impossible for him to pick up his back leg on that side. This is especially helpful if someone is trying to bandage a back leg.
So that's about it. It's basically just staying alert and in a position where you can control your horse and protect your vet and yourself if something unexpected happens. And even if your horse is very kind and laid back, you should still follow this protocol. In the first place, it's just as easy to do it this way as any other way. Even if your horse never does anything, it hasn't cost you a thing to practice this. And just in case anything totally out of character does happen- you, the vet, and your horse would still be safe. But beyond that, ESPECIALLY if your horse is great, it's a good idea to practice this. Because, unless you're planning on never owning another horse, your next horse might not be so accommodating. He might be the perfect horse, but have a needle phobia. So by practicing on a calm horse, it'll be much easier to deal with a more excitable horse next time. One day you might be out on a trail ride with a friend and their horse pulls his shoe half off, or gets tangled up in wire and you need to hold the horse while they fix the problem. Their horse might not be nearly as nice as yours. It would be good to know that you could step up and handle the situation if you were needed, wouldn't it? I've been using this method for 40 years now and it has allowed me to handle even rank, panicking horses with the maximum amount of safety possible. I highly recommend it.
Thanks for your time. I hope this information was helpful. If anything here was not clear, or if you have further questions, please feel free to ask. I'm new to writing, and I found it much more difficult to describe this method in print rather than just showing someone how to do it using an actual horse.