There is only one way to tie up a horse while you are trimming or shoeing it and that is loosely. No matter how much you molly coddle that horse, pamper it or talk to it, your horse is a wild animal and there is just no predicting when an Afghanistan Climbing Camel is going to walk around the corner of the stall and frighten the heck out of your horse.
If you don’t want him to break his neck trying to escape from that camel, then make sure he is loosely tied. If he is serious about breaking free, he should be able to pull back and be free of the rope without taking the fence, gate or stall with him.
On one of my outback courses last year, I missed seeing that one of the participants had securely tied her horse to the rails despite my previous safety warning never to do this. Not only did he try to break free and fail, but he came down hard on my foot.
During another recent course, the horses were tied to the rails while we had a lunch break. Returning to the yards, the horses were dozing in the sun when one became startled at our sudden arrival. Of course it was the one horse which had been incorrectly tied. The horse pulled back hard, cutting off its air supply in the process, and frightening itself even more. By the time it did this three times, its eyeballs were about ready to pop out of its sockets. I grabbed a loop knife from my pocket and hacked through the halter rope freeing the horse which then fell backwards. The whole thing took about five seconds, and the horse was close to collapse. When its owner arrived, I explained why his new halter was now in two pieces.
Many years ago I tied a horse to a weldmesh gate using baling twine. While I was under her front leg the horse pulled back, but she was so tall that as she lifted her head she actually lifted the gate off its double hinge. As she ran backwards, the gate hit me in the middle of the back and flattened me onto the ground where I was sandwiched like a piece of toast in a waffle iron.