See N Spots, I'm not sure how it works either, but my gelding used to be ouchy walking across the gravel road when he was first barefoot, now he will stand on it, and trot down it on his own with no stumbling or acting like it hurts him. But really, I don't have much knowledge on the subject, this is just personal experience. It did however, take him about 4 months to toughen up.