39 s center of mass on the putter the u201c sweet spot u201d is centrally located on the hitting surface to properly use the putter it is necessary to roll the head across the putting surface on the freely rotating ball the ball guides the head to move in a straight line furthermore the ball assists the golfer to maintain the head at the proper level above the putting surface it is necessary for the golfer to have the ball touch the putting surface to cause rotation of the ball in a putting swing when the ball is touching the putting surface and rotating the sweet spot of the hitting surface will strike the targeted golf ball additionally the putter helps the user develop a desired putting stroke by controlling the speed of the back stroke when the head is swung away from the golf ball and front stroke when the head is swung toward the golf ball the ball of the putter only spins within a desired speed limit of the back stroke and front stroke if the stroke is too fast beyond the predetermined limit the ball will not spin the user can know whether the ball is spinning by looking at the broken line on the ball if the line remains broken the ball is not spinning if the ball is spinning the broken line will appear as a solid line which is in line with the sight line of the top surface of the head when the average golfer properly uses the putter his.