Whenever my horse is having a hard time getting to know something scary I always start from the ground and work my way up. It helps build my confidence and his. It also helps keep anxiety low for both of us. G&S is right in not tensing up when you get close to the rail and expect something to go wrong. Stay firm in what you are asking. But getting back to starting on the ground, I start in the middle lunging and slowly let him get closer to the rail. If he starts to shy away then I move back, to where he will actually go around in a circle, from the rail and make him work harder. As soon as he focuses back on me, that’s the goal of the exercise, I can give him a reward of getting to walk or go slower. As long as he is paying attention to me then I can move him closer to the scary object until he is passing it without thought. After he is good with one side, I START back in the middle going the opposite direction. I don’t want to rush him and send him back in panic. And then I repeat earlier steps to work his other side. My horse is an Appendix and he shows his thoroughbred side most of the time so he gets really nervous and distraught at times. He responds really well with taking things slow and getting a rhythm that makes him feel comfortable. All horses are different and you know how your horse ticks so your judgement is the best as to what you should do, but I have always found a foundation from the ground to be much more stable and safer for all who are involved. That’s how my mom trained her horses and that’s how she taught me and I realize that it is my way and not precisely your way. So I wish you the best of luck in getting this fiasco figured out. Happy Trails!