Snaffle bits come with several different mouthpiece options — a mullen mouth, which is straight, and either a single or double jointed mouthpiece.
It’s important that the mouthpiece be configured in the proper way for the bit to work properly. Since many bits are made with ring cheek pieces, it can be inadvertently attached to the bridle incorrectly and will cause a lot of pain to the horse.
When a snaffle bit has jointed mouthpiece, it is important that the joint drape downward. This allows the bit to fit into the bars of the mouth (where the horse has no teeth) and drape over the tongue.
If the bit is attached to the bridle backwards, the snaffle joint creates a sharp angle because the joint is bent in the
wrong direction. If the rider were to pull on the reins when the bit was backwards, it would drive the joint into the palate of the horse’s mouth and cause pain.