Cherie, thanks for a lot of good info!
Man, I guess a few "well-broke" horses who bolted with me & ran through the two-rein pull weren't so broke after all! :)
Bsms, I don't want you to have a horse at any level run off with you & you're only making it worse by pulling back on both reins. Hopefully, if it happens, you'll remember this discussion & simultaneously learn that it ain't working!
I believe that a rider should also know the pulley-rein stop, as taught by Julie Goodnight, because unless a horse has the one-rein "infallibly" on him, so that he stops without having to have room to circle in, like on a narrow trail, one is in trouble. Google for video of Julie's pulley-rein stop, for narrow trails & such! :)