The fence or the wall of an arena is not considered an outside aid.

Many times the rider, unknowingly, allows a fence or wall of an arena to be substituted for his or her outside leg and outside rein aids. To make sure you are using all aids, imagine a railroad track 5-10 feet off the wall, or fence, and practice keeping your horse straight between the rails.

Always practicing riding off the wall will assure that the rider is using the proper aids when they have to ride on the wall or fence.