The problem with snapping the
reins directly to the snaffle bit is that if the horse should "freak" or fight
violently, as horses occasionally do, serious damage could be done to the mouth
and tongue. By snapping the end of the reins on the upper halter rings
(next to the cheek) and then running it through the bit, down through the front
legs and up over the back -- if the horse does have a problem it won't do mouth
damage. You get the same action through the bit when the horse moves, but
a little lighter.
Another thing ...
there should be enough slack in the lines so when the horse has its head in
a natural position there is no pressure . The horse I used this with
learned not to flip his head when he felt bit pressure and was much easier
to work with under saddle.
I school all my horses in the roundpen, and I use long reins, surcingles,
and do ground driving. I had a good trainer teach me a method that was very
similar to the one Karen described, however we snapped the reins to the
snaffle bit rings. Each movement of the horse, causes a little gentle downward
tug, and the horse rewards themselves by giving.