Tried one years ago, with a keen jumper. It was horrible, he hated it, fought it harder. Eventually, I went into a simple gag snaffle, with two reins. This is now where I go when I have a horse who wants to try to tow. Off the track racehorses have been taught and encouraged to pull down on the rider, balancing himself on the rider’s hands- they are the classic type of horse who would want to tow in their second career- though any horse who has been ridden this way previously can learn the habit too. The gag snaffle with two reins (regular snaffle rein, and a pulley rein) acts like a regular snaffle, until the horse attempts to pull down and tow. The mouthpiece is soft and inviting, and comfortable for the horse as a regular snaffle. When the horse attempts to pull down and tow the rider, the pulley rein comes into effect, and turns the angle of pressure in the mouth, shifts the pressure from the bars of the horse’s mouth (where he CAN pull from, and WANTS to put the pressure so that he can haul on you), to the corners of his mouth, where he CAN’T pull from, and instead his head is raised, instead of pulling down on you. The rider does nothing, just holds the two reins normally, with an educated, giving hand. It is the horse who uses the bit, not the rider. After trying out his regular “tow the rider” habit, and finding out that it simply no longer works for him the same as it did in the past, the horse usually loses the habit in time, and becomes a softer horse to ride. When the habit is extinguished, the horse can often switch back to the use of a regular snaffle.