The Fitting Rule provides a direct and instant reading of driver and 5-iron length on the same ruler, which is made of top-quality aluminum with heavy duty, baked-on epoxy letters. Simply have the golfer stand with arms and hands relaxed at their sides, then measure from the wrist (the major fold of skin at the base of the hand) to the floor. Wrist-to-floor measurements are considered more accurate than fingertip to floor because the hands are closed around the grip.