Originally Posted by Tnavas
Just dressage it - great information but will disagree with your description of the action of a single jointed snaffle - it does not dig into the roof of the mouth - it is impossible for it to do so unless the horse has it's head very high with nose pointing to the sky and the pull on the rein is downwards. The horse holds the bit in position, by the pressure of its mouth around the bit, the joint hangs downwards an doesn't rotate upwards when the rein is used. When the rein is used the action on the bit is to fold applying pressure to the lips and bars only.
I have to disagree due to simple physics. Once you begin to put pressure on the reins, the bit will
pivot in the mouth so that the apex of the joint will be directly opposite of the pressure being applied. So, on a horse that has been taught to give to the bit and break at the poll, a rider who pulls hard will cause the joint to stand up in the horse's mouth, pointing directly at the palate, so yes, it is
possible to stab the horse in the roof of the mouth with a single jointed snaffle bit.
Those horses who fling their head up in the air and root their noses out do so because they have figured out that doing that is the only way to negate the function of the snaffle. Once their head reaches a certain angle, then the joint will be pointing downward in their mouth toward their front teeth. After that, the only pressure they are getting at all is on their lips and horses that have figured out the "magic spot" for a snaffle generally find that lip pressure rather easy to ignore.