 As a result, the thin edge of the center link can press into the tongue, creating a very small bearing surface.When a full-cheek Dr. Bristol is used, the bit can be rotated so that the angled middle joint lies flat with its broad side against the tongue; when used this way the bit is relatively mild.This latter method is only possible because bit keepers ensure the bit stays in a fixed position in the horse's mouth, and thus bits that do not use bit keepers (e.g., a D-ring or eggbutt) do not have this milder option.