releases and returns to its unstressed unflexed position pivoting arm 38 is now located slightly above the horizontal weight extension shaft 48 is inserted into the end of arm extension 40 the arm extension set screw 47 is tightened to hold the weight extension shaft 48 in place in the arm extension 40 next donut weight 50 is applied to the weight extension shaft 48 until pivoting arm 38 moves back to the horizontal position and flexes golf club shaft 10 at this point golf club shaft 10 is flexed and is free to flex back and forth as golf club shaft 10 is rotated via the rubber wheel 30 the horizontal position of the pivoting arm 38 is determined by the flexing of golf club shaft 10 in reaction to donut weight 50 in position on the end of weight extension shaft 48 previously the horizontal position of the pivoting arm 38 was determined by the weight support set screw 44 once again the dial indicator 52 is set at the zero position to set the dial indicator 52 at the zero position the rotatable bezel 56 is rotated until the dial indicator 52 reads zero this is the reference position of the golf club shaft 10 to determine the location of the spine 16 the rubber wheel 30 is rotated by hand until a position of minimum deflection is indicated by pointer stem 54 on dial indicator 52 it is a very distinctive tactile sensation the rubber wheel 30 is continuously rotated until golf club shaft 10 assumes a position of minimum deflection which is the position at which spine 16 is at the top dead center position of golf club shaft 10.