I have had several colts and Stallions but this one is really trying me. He is such a good boy at home that we do everything in just a headcollar but get him to a show and he turns into the devil. I can handle him hanging his willy out as I think time would make him better but it is when he is stood on line he starts to rear. I just don't know how to stop him from doing it and don't like taking him out as it upsets the other horses in his class. Anyone got any ideas or has had this situation with a young colt?