How Snaffle Bits Work

prevent the bit from slipping through the horse's mouth. Large leather or rubber type discs can be used to keep the bit from chaffing the sides of the horse's mouth as well. The rings can affect the weight of the bit and prevent the bit from pulling sideways through the horse's mouth.​
How Mouthpieces Differ
Bits with jointed mouthpieces will have a nutcracker effect, while straight mouthpieces spread the pressure evenly over tongue and bars. An egg butt snaffle will have oval rings, and the mouthpiece will get thicker as it approaches the rings. These bits are among the mildest because they distribute the pressure of the rein aid over a wider area of the bars. Generally the thicker the mouthpiece the milder the bit. A horse with a large tongue or low palate might be uncomfortable in a bit with a thick mouthpiece.
The French link is considered the mildest jointed snaffle. The Dr. Bristol link, although it looks similar, is much more severe, because of the way the plate in the middle of the bit lays in
 
constant contact with the tongue—either flat or on an angle, depending on how the rider attaches the bit to the bridle.
Variety
Snaffles can be hollow to reduce weight, flexible, twisted, ​joined with one or more links, have keys or rollers, be squared or oval, or have any combination of shapes and joints. Mullen mouth bits are the same width from end to end. Wire bits are quite thin and wire wrapped bits add to the sharpness of the pressure on the bars of the mouth.
All of these variations are intended to enhance the rein aids. Different metals and material can be used to encourage the horse to accept the bit for its taste or encourage salivation. Copper, sweet iron, vulcanite, and other synthetics can be used. Some bits, often used for teaching a young horse to hold the bit, are flavored.
The Vesatility of Snaffle Bits
Snaffles are often the first bit a horse will carry. Many will be ridden throughout their entire lives with a snaffle bit.