The Shanks
The Shanks
The shank is where the reins connect to the curb bit. The top of the bit is then connected to the headstall. When the reins are pulled, it brings into action the mouthpiece, puts pressure on the curb strap, and pulls the cheekpieces of the headstall, bringing pressure on the poll.
All shanks work on the same principle. When the rein is pulled the butt (where the shank connects to the mouthpiece) rotates the mouthpiece and activates the pressure points.
The curve or ratio of leverage in the shank, and to a lesser degree, the length of the shank determines how it affects the pressure points. The more leverage, the faster the reaction time from the hands and reins to the mouth. The greater the curve, the less leverage or pressure.
The Curb Strap
The curb strap is often mistakenly thought to just hold the bit in place. In actuality, pressure from the curb strap acts on the sensitive area under the horse's chin. This area has avery thin fat layer and very sensitive nerve endings. When the reins are pulled it puts the chin into a vise like grip between the curb strap and the bit.
A general rule is that the curb strap should be loose enough so that two fingers fit between it and the horse's chin.
Curb straps come in several varieties (listed in order of severity from least to most):
