A saddle must be measured for width, length, and front arch height (clearance over the withers). In ideal circumstances, the saddle is tried on the horse prior to purchase, or is purchased with a return option if it does not fit. When saddle shopping, or if having a saddle custom-made, one method of sizing the horse is known as a "wither tracing." To create this, an artist's flexicurve or a piece of coat hanger wire is placed up over the withers about two inches behind the horse's shoulder blade, then shaped to fit across the withers. The shape is then traced onto heavy paper or cardboard. An average horse can be fitted with just this measurement by comparing the angle of the wither tracing to the angle of the piping at the front arch of the saddle. However, horses with an unusual shape are measured in three locations, the second measurement approximately two inches behind the first one, and the last measurement nine inches behind the withers. Often for accurate measurements, a professional saddle fitter may need to be consulted.