Curb bits are not for young, green, or inexperienced horses due to their often-indirect and advanced action; rather, horses must be transitioned into them gradually as broke-ness, finesse, and responsiveness increase. Curb bits differ from snaffles in that they apply leverage pressure in the form of a curb strap or chain. The shanks increase the amount of pressure that is applied to the mouth, magnifying the hands’ action. When the reins are pulled, the bit rotates in the mouth. The mouthpiece engages more fully as more pressure is applied, the curb tightens, and when it has tightened as far as it can go, strong pressure is applied to the mouth. Curb bits will also apply some degree of poll pressure, though for most this is very minimal. Generally speaking, the longer and straighter the shank, the more the pressure is magnified, and the harsher the bit. A long purchase (the upper part of the shank between the mouthpiece and bit hanger) also increases leverage and severity. A long, curved shank bit gives some warning in between the time the reins are picked up and the bit engages, while a short, straight shank bit engages almost immediately. Mild curb bits are great for teaching collection, flexion, and lateral movement. A short, curved-shank curb with a three-piece or snaffle mouthpiece is good for introducing a young horse to leverage pressure without scaring him after he has graduated from a snaffle. A curb with a solid or correctional mouthpiece is considered “the” bit for broke Western horses who know how to neck-rein—there is no direct reining here, as the fixed shanks do not allow for independent side movement.
In terms of curb construction, the mildest is flat leather, followed by rawhide, double chain, single chain, and finally the severe “power curb.” A tighter curb means the mouthpiece will engage sooner. Gag Bits
Gag bits (called elevator bits in the English world) seem to have a negative connotation, perhaps because their name conjures up images of a horse spitting and choking on a too-tight mouthpiece. In fact, when used correctly, gag bits can be quite mild. I personally like them (and Wonder/Half-Wonder bits in particular) for teaching collection, flexion, and lateral movement to a green horse moving out of a snaffle. Gag bits are popular in the training pen, barrel racing and in gaited horse communities.
Physically, they are composed of the mouthpiece (often a chain or snaffle mouth), shanks of varying lengths, and a curb. What sets them apart from ordinary curb bits is that the mouthpiece is not fixed in place—it is free to move and slide about. This is the “gag action.” When pressure is applied via the reins, the bit rotates and the mouthpiece slides around the ring. When the curb has tightened as much as it can and/or the mouthpiece reaches the end of its track, increasing pressure is applied from the mouthpiece. Poll pressure is also applied as the curb mouthpiece slides and the bridle effectively shortens. This gag action gives the horse plenty of warning from the time the rider picks up the reins to the time harsh pressure is applied. It also allows for independent movement of the shanks, meaning you can “pick up” one side of the horses head without affecting the other—great for lateral movement.
English elevator bits are often used without a curb, making them similar to draw bits, which will be discussed later. Draw Bits
Draw bits consist of an unshanked bit with two rings through which a rope, cable, or curved piece of metal is run. The reins are attached to the end of this. A piece of leather, rope, cable, or wire (in order of increasing severity) is run behind the ears and attached to the cord running through the bit. When the reins are pulled back, the cord is also pulled, tightening the rope behind the ears (poll pressure) and lifting the bit. The bit slides along the cord until it can go no further. The bridle shortens, and increasing mouthpiece pressure is applied.
If the draw bit also has gag action and a soft ope is run behind the ears, this is a very mild bit and good transition from a snaffle, especially for teaching lateral movement. If the bit is more snaffle-like, has a harsh mouthpiece, or a cable or wire is run behind the ears, this bit can become quite severe. Draw bits work well on soft-mouthed horses, young horses, or those who don’t respond well to curb or noseband pressure. Combination Bits
Combination bits (sometimes called bitted hackamores) consist of a curb bit (almost always a gag bit) and a noseband made of leather, chain in tubing, rope, rawhide, bike chain, or twisted metal (in order of severity). They work best on seasoned horses who already know their jobs and do well with a little guidance, but do need some help steering and stopping. There’s a lot of action and a lot of different moving parts in a combo bit, so it can scare off a young or inexperienced horse.
When pressure is applied, the action is the same as that of a curb or gag bit, but additional pressure comes from the noseband, which presses down on the face. Adjusted too low, the noseband can damage the nasal bones, but adjusted properly it encourages the horse to rate or sometimes drop its head. Most combo bits aren’t incredibly harsh, because the pressure is distributed across so many different places. However, those with severe nosebands, harsh mouthpieces, or long shanks can be quite brutal. Most horses don’t need all the extra action and control provided by these bits and will only be confused by all the stuff going on. Most combo bits should only be used by skilled, experienced riders on very well trained, broke horses. Lifter Bits
Lifter bits combine a tiny amount of gag action with a long purchase. They’re fairly harsh, particularly when combined with a severe mouthpiece, and are used for encouraging a broke horse to “lift” his nose—lateral movement. Lifter bits are popular with barrel racers who need to get their horse’s nose quickly during a run.