How Snaffle Bits Work

When the reins are pulled, a ​pressure is applied to the area of the gums that have no teeth called the bars of the mouth. This gap is between the front teeth that crop grass, and the back teeth, that grind the food. A properly fitting bit sits comfortably within this gap, just forward of the grinding teeth. Occasionally, a horse will have problems carrying a bit comfortably and small teeth called wolf teeth may have to be pulled, or a bit seat created.
How the Horse Reacts to the Signals
The simple snaffle applies pressure to the bars of the horse's mouth. There is no pressure anywhere else on the horse's head and no leverage comes into play as it does with a curb bit. When you pull straight back, the horse will understand that equal pressure on both sides of its mouth means to stop. A pull to the right,
 
that applies pressure on the right bar, means turn to the right and a pull to the left, of course, means turn left.
As you learn to refine your rein aids, combining them with using your seat and leg aids, you will learn to cue your horse for things like leg yields, half-passes, lead changes, changes of gait and other more advanced riding skills. While at first you may be simply 'pulling' the reins, you will in a short time learn to give much more subtle signals that can be felt by the horse but are almost imperceptible to the average observer.
The Function of Bit Rings
The rings on a snaffle may be D shaped or have a small piece sticking up or down like a full cheek snaffle and Fulmer snaffle. The rings may slide or they may be fixed to the mouthpiece. The shafts perpendicular to the mouthpiece on the full cheek and driving bits