Neck reining is when you direct a horse by the feel of the reins on its neck.  Well-trained horses are very responsive.  You can easily control where they go.  You can rein with one hand.

On a colt, you have to use two hands.  When you want to turn to the right, slide your right hand down the reins closer to the horse’s head.  Then with both of your hands at the same time, you pull the reins over to the right.  To turn to the left, you do the exact opposite motion.  You slide your left hand down the rein and pull with both hands.  The most important part is moving your hands together in one smooth motion.

You do not have to be riding a horse to practice this movement.  You can stand up or sit down anywhere and pretend you are riding a colt.  Practicing the movement so that your hands move together will help your horsemanship skills.