The Trouble with Tom Thumb
As a trainer and clinician I am always being asked a variety of horse-related questions. I think the single most common one asked, however, is "what kind of bit should I use on my horse?"

In my situation, if I need to do any training on the horse whatsoever, I use a simple full-cheek snaffle bit. If the horse is well-trained and responsive, he stops, backs, and neck reins all on a light cue, then I use a curb or grazing bit. These are the only types of bits that I use on a regular basis, and are the only ones that I feel comfortable recommending.

There is one bit that I never recommend, however, and in fact do my best to try to talk people out of using, particularly if they are experiencing problems with their horses - problems such as unresponsiveness while stopping, backing, or turning, or even more severe problems like head tossing, shaking their heads, or rearing. The bit that I am talking about, and which is often the source of such problems, is the Tom Thumb snaffle.

In Picture A, shown from left to right are a full cheek snaffle bit, the Tom Thumb bit, and a grazing type curb bit with a leather curb strap.

TRANSITION BIT
The Tom Thumb snaffle was originally designed as a transition bit that was to be used in Western training. When a green horse was far enough along that perhaps a training snaffle was no longer necessary, but not far enough along to be moved into a curb bit, the Tom Thumb would be used. This would be great, if in fact, it made the transition simple and easy. Unfortunately, it doesn't. The truth of the matter is that, due to its design, it could possibly be considered one of the worst bits that somebody could use at a highly critical time in a young horse's training.

The Tom Thumb is commonly termed a snaffle bit because its mouthpiece is broken, or hinged, which is a trademark common to the true snaffle bits. That is where the similarities end. On a true snaffle bit, the reins are attached to a relatively small, swiveling ring which could be considered a working part of the mouthpiece itself. When the rein is pulled, as you would do when asking the horse to turn, the ring that the rein is attached to moves completely away from the horse's mouth. The mouthpiece itself slides in the same direction, which causes the ring on the opposite side of the horse's mouth to apply pressure on that side. Because the horse is taught to go away from pressure, it then makes sense that if you are pulling to the left, and thre pressure from the bit is on the right side of his mouth, he will naturally turn his head to the left. This is the simple principle that is commonly referred to as direct reining, or "plow reining". It is also a principle that is almost impossible to perform properly with the Tom Thumb, due to its design.

SHANKS PROHIBIT DIRECT REINING

Unlike a true snaffle bit, the Tom Thumb has shanks similar to the ones found on a solid curb bit. It is to the bottom of these shanks that the reins are attached. The headstall is attached to the top of the shank, as is some type of curb strap which fits around the bottom of the horse's jaw, in the chin area. These shanks swivel and are attached to the bit's mouthpiece.

It is that one flaw in the bit's design that renders it almost totally useless when it comes to any kind of training which involves direct reining. Again, using direct reining in a snaffle bit, the horse is taught to move away from pressure. To turn to the right, the pressure is on the left side of the horse's mouth. To turn to the left, the pressure is on the right. There should be no other pressure being applied by the bit that could cause the horse to become confused.

Unfortunately, confusion is precisely what happens to a horse when the Tom Thumb is used. Because of its shanks, any attempt at direct reining results in pressure on several different areas around the horse's mouth. For instance, if you are asking the horse to turn to the left, you will be pulling on the left rein, with the idea that the pressure from the bit will be on the right side of the horse's mouth, thereby turning the horse left. However, because the rein is attached to the bottom of a swiveling shank, pulling on the rein results in the shank turning and tipping into the left side of the horse's face. When the shank tips, it also shifts the mouthpiece, which, in turn, puts pressure on the right side of the horse's mouth by pulling the right side of the bit into it. You now have pressure on both sides of the horse's mouth, as well as a shifting of the mouthpiece inside the mouth.

If this wasn't bad enough, tipping the shank also results in the tightening up of the curb strap that is under the horse's chin. Suddenly, the simple act of asking the horse to turn to the left is no longer a simple act. The bit is applying so much pressure in so many places, that the horse has no clue as to what you were asking for in the first place.

He then tries to tell you that he doesn't understand what you want by twisting his neck and shaking his head. Of course, we look at this as him being belligerent and not wanting to do what he was told. So, we simply apply more pressure to the rein which resluts in an even bigger fight on his part.

Eventually, the horse does finally turn to the left - but only as a last resort. Before he does, he will first try several different options. Among these will be: 1) turning to the right, because the left shank tipping into the side of his face is forcing him that way; 2) lifting his head as high as he can get it; 3) dropping his head as low as he can get it; 4) backing up. Rearing is also an option which sometimes happens as well.

The rider is beginning to pick up the left rein in Picture B.

Even though there is still slack in the rein, you can see the left shank of the bit is beginning to put downward pressure on the headstall (which transfers to pressure over the poll of the horse). The left shank is also beginning to pivot on the hinge in the bit, indenting the horses face just below the cheek teeth. The curb strap is already fairly tight on the left side, even with this slight pressure on the rein. The mouthpiece is beginning to create a "V" inside the horse's mouth as the joint in the center of the bit begins to collapse.

Picture C shows a horse's typical response to a simple request to back up when using the Tom Thumb bit.

The left shank of the bit has turned into the horse's face, and the curb strap has tightened. The horse is opening his mouth in confusion, and in an attempt to eliminate the pressure.