Half pass, travers and renvers and are all excellent exercises for developing suppleness, performed in different places in the school.
Introduce travers with care or your horse will not produce travers but a twisted contortion. Start at the beginning of the long side of the school and maintain a slight inside bend with your inside leg. Do not over bend the horse. Lightly touch with your outside leg back to bring your horse's quarters to the inside. As with half pass use intermittent touches with your leg, and only use the leg as necessary so you don't rush your horse in the movement. Don't over bend them to the inside or the outside shoulder will fall away.
The wall on the long side can prevent forward movement, to resolve this ensure your horse is carrying the movement from the inside hind leg not the inside shoulder.
Renvers is the reverse of travers, the quarters are to the wall and the shoulders are on an inner track with the horse bent in the direction of the movement. To position your horse for renvers, turn on to an inner track on the long side of the school. Change to bend towards the outside of the school. As with travers use your outside leg (outside to the bend, which will be on the inside of the school) to move the horse's haunches towards the wall.
Travers and renvers can be ridden on a circle and are both very beneficial to the development of a horse’s suppleness, engagement and collection. Care must be taken to ensure that the horse is correctly round the rider's inside leg and not just crooked.
The picture below shows the position of a horse in half pass, travers and renvers. The red line represents the wall and you can see how in each exercise the position of the horse is the same.
Diane Followell Classical Dressage Trainer