To flex the jaw in direct flexion, first start the horse into a walk. Never let the gait slacken during flexion. Close the legs. When the horse goes up into the bit, close one hand on one snaffle rein (if the movement is done with a snaffle bit), or close the hand on both curb reins. Do not make the pressure of long duration if resistance is encountered. Alternate the action, first by releasing, then increasing the pressure. This is more uncomfortable to the horse than continued pressure, and he will soon yield.
The head is flexed in direct flexion so that it is set with the front line of the face nearly vertical by the action of both curb reins. The head and neck are raised by the snaffle bit, should they be lowered too much.
Lateral Flexion.—Lateral flexion is a concession which the head and neck make by turning the head to the right or to the left when an opposing action of the reins stops an extension of the neck. The jaw gives in lateral flexion as in direct flexion. The neck gives by making the head make a turn of a quarter of a circle to the right or left at the poll.
Lateral flexion should be demanded, in the beginning, at the walk. To obtain it, to the right, for example: first, resistance must be offered by the right direct rein, which leads the head into the desired position; the left rein then acts to limit this movement and to work together with the right rein to obtain the concession of the jaw.
Flexion may be made dismounted, if absolutely impossible of execution mounted.
Direct Flexion Dismounted.—Stand on the near side of the horse. Take the snaffle reins off the neck over the horse’s head and hold them a few inches in front of his head with the left hand. Urge the horse forward into a walk and raise the head slightly to the proper elevation with the snaffle reins. When the horse moves out at the walk, take the curb reins in the right hand and assimilate the movement of the reins as though flexing the jaw mounted. Do not let the horse slacken speed or, at any cost, back up.
Lateral Flexion Dismounted.—Stand on the near side, with the snaffle rein held as for direct flexion. Execute direct flexion and when performed lead the horse’s head to the right with a snaffle rein, increasing the pressure of the right curb rein slightly until the head is turned to the right at the poll. Do not let the horse move backward, nor let the neck flex in rear of the poll. The maximum movement of the head is over an arc of a circle of 90 degrees.