The “pull and slack”, that was what I learned first. We would put a Hackamore on a colt, tie a long rope to the end of the reins, turn the colt out in the square pen (about 40 feet across) and when he took off, Buck would wrap the rope around his hip and “double him”, immediately releasing the rope as soon as the colt “swapped ends.”
This was repeated enough times that the colt began to move at a steady trot without trying to bolt away, but miraculously it usually only took three or four doubles on a side. After that, only the lightest tug on the rope would cause the colt to sink his hocks into the ground and stop. I didn’t know about “round-pen” or “liberty” work in those days. But the effect was similar, because the colts learned pretty quickly to “pay attention” to a human being as they loped or trotted circles, frequently turning around to strike off in the opposite direction. Never was the colt allowed to “lean against” the bozal, ( bo-SAHL) the rawhide noseband, for that would encourage him to “bull into it” later. And once I was actually aboard a colt, later on, the main thing I would hear from Buck was “Don’t hang on their head!” He advocated “doubling” or turning them back on the fence instead. Colts rapidly learned to work on a loose or “draped” rein this way. It was never brutal, and the psychology was that which is now called the “one rein stop” very “en vogue” In natural horsemanship. Buck – using an ancient method, was a man ahead of his time.