François de la Guérinière
If a horse refuses to move sideways in one of the two directions, it is a sign that he has not been rendered supple enough on the opposite side.
…the shoulder-in means controlling the outside much rather than driving the inside.
Only when the horse is calm and confident can he give the rider his impulsive forces which the rider can then use at will.
Nuno Oliveira on Half Pass
Renvers is the final exercise in this quartet of lateral movements with shoulder-in, half pass and travers. Like travers, it is the same as half pass, but this time it is performed down the side of the school with the horse’s shoulders to the inside and, unlike shoulder-in, the bend is in the direction of the movement. If the travers and half pass are well established, renvers is a natural progression of these movements.
One way to start renvers is from half pass. Begin with a good well balanced half pass. As you approach the wall, gently step the quarters over a little with your outside leg, while slowing the shoulders with your inside rein towards the neck. Do not pull the rein back as this will block your horse’s hind leg and place him on the shoulder. The rein and leg action will advance the quarters the track, and once the quarters are on the track, maintain this position and angle down the side of the school.
An alternative method is from the long side. Ride a good corner so your horse is well balanced on the long side of the school. Change the bend to the outside and then bring the horse’s shoulders in with a delicate movement of the hands towards the inside of the school. The outside leg sends the outside hind leg under the horse’s body.
With some horses I find that transitions between shoulder-in and renvers have a good suppling effect and can significantly engage the quarters. To ride this, start in a good walk shoulder-in and then after several steps, change the bend so the horse is positioned in renvers. Be very careful that you can retain the balance or the horse will drop into the shoulder again.
Diane Followell Classical Dressage Trainer