Different bits employ pressure on different parts of the horse's head in
order to achieve the desired result. The places where bits can act are:
1. the tongue
2. the bars
3. the lips
4. the roof of the mouth
5. the chin groove
6. the nose
7. the poll
8. the side of the face
In general, thinner bits are harsher by applying pressure over a reduced
area, while fatter bits are milder by applying pressure over a wider area,
however some small-mouthed or thick-tongued horses are uncomfortable with a
thick bit, as they do not have enough room in their mouth for it.
Loose ring bits are supposed to give more "play" in the mouth, encouraging
salivation, which lubricates the mouth and makes it softer, whereas fixed ring
bits are more precise in action than the loose rings.
Copper and steel/iron mixtures (sweet'n'sour bits) encourage salivation by
varying "tastes" of the metal, as in the cherry roller, which also provides play
in the rings. Breaking bits have smooth "keys" to encourage play, which is fine
when introducing a youngster to a bit, but not favourable for riding in, as it
can distract the horse from the job in hand. Nylon and rubber/vulcanite bits can
be too dry for some horses, causing sore mouths from rubbing. Vulcanite is
hardened rubber.
