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Buck teaches the pitfall of the human yielding to the horse instead of the horse yielding to the human. He also talks about the importance of watching the whole horse, and not just one part of the horse.
Buck demonstrates the technique for using a flag to control your horse's front end and hind end.
Buck demonstrates the difference between a horse being responsive to a flag vs afraid of a flag as he uses the flag to guide his horse under saddle.
Buck demonstrates walking down the arena while having the horse yield the front and hind.