bit

A stainless steel, rubber or aluminum bar, attached to the bridle, which fits in the horse's mouth and is one of the means by which a jockey exerts guidance and control. The most common racing bit is the D-bit, named because the rings extending from the bar are shaped like the letter "D." Most racing bits are "snaffled," (snaffle bit) which means the metal bar is made up of two pieces, connected in the middle, which leaves it free to swivel. Other bits may be used to correct specific problems, such as bearing in or out.