Dressage Arena Letters and Dimensions - thesprucepets No matter how you ride, arena letters are useful. If you ride western and never plan to ride a dressage test, arena letters can help you plan your schooling mark the outside of your riding ring and give you focus points so you can make turns, circles, and other maneuvers more accurately. Arena Letters | Dressage Extensions No dressage arena is complete without a set of letters! Dressage Extensions offers a great selection of dressage letter sets in all forms to suit every need. Choose from lightweight metal letters than stick in the ground to vinyl rail- or wall-mounted letters or tower letters than can be filled with flowers.