There may come a time when your horse is so strong that you must apply a pulley rein in order to stop the animal. This is a powerful, emergency rein aid that should be practiced before you have a real need for it, for if it is applied incorrectly, it will not only be ineffective, but can be dangerous.
First, make sure that your reins are quite short. Then place one hand in the dip in front of the horse’s withers, while SLOWLY pulling back with the other hand. (Note: A quick jerk on the reins can flip the horse backwards.) The fixed rein position of the hand placed in the dip gives your other hand added force when you pull back. You should be sitting during the application of the pulley rein, so that your seat and back reinforce your hands. Also, the hand in the dip MUST REMAIN FIXED. If this hand slips and you’re only pulling back with the other hand, you could cause the horse to fall on its shoulder. (Look at some old cowboy movies and watch how the stuntmen cause their horses to fall by pulling hard on a single rein.)
The pulley rein should be so familiar to all levels of riders that it’s application is automatically correct when the need arises.

The rider applies a pulley rein by firmly placing one hand in the dip just in front of the withers, while pulling back smoothly with the other hand.