the putter generally indicated at 20 has a head 21 , and a shaft 22 terminating at its upper extremity in the grip 23 . the top surface 24 of the putter head is provided with a series of converging reference lines 25 , and the central reference line 26 preferably located directly above the impact center of the club head 21 . this configuration is described and claimed in my u . s . pat . no . 4 , 659 , 083 . the present invention utilizes this configuration in conjunction with a reference rod 27 , which can be laid upon the ground so that the putter head can be stroked above it as shown in fig1 . while the illustrated pattern of converging lines is the preferred arrangement , a single full line , or even a short central line or dot on the top surface of the putter head can be made to track visually along the reference rod , as seen from above . these short reference marks , however , do not clearly indicate angular deviation of the head . the position of a ball which would be struck , if it were present , is indicated in dotted lines at 28 . the striking face 29 of the club head is in a plane perpendicular to the reference rod 27 , which is laid on the ground to simulate a selected direction of ball travel . the reference line 26 and the rod 27 should be of the same color , and of comparable width . with the alignment shown in fig1 a ball should proceed along this line . this condition is illustrated schematically in fig1 . it has been recommended by some who have studied putting seriously that the player practice has stroke coordination without the ball being in place , and the present system is ideal for this . after the stroke has been refined and reduced to a habit pattern of muscular responses , the ball may again be used . the inital practice should apparently also be without reference to a hole , so that all attention can be put on the stroke to the exclusion of distractions . referring to fig8 , and 10 , various possible positions of the club head and path of swinging movement are illustrated . in fig8 the path of swinging movement of the club head is causing the point of impact on the club face 24 to move in the vertical plane containing the reference rod 27 . the club head , however , is rotated slightly clockwise with respect to the position shown in fig1 causing the club face 29 to be &# 34 ; opened &# 34 ;. in fig8 the club head is shown in an opposite displacement , with the club face rotated counter - clockwise , to a &# 34 ; closed &# 34 ; position . in addition to the angular displacement of the club head from that shown in fig1 the path of movement of the club head indicated at 30 is at an angle with respect to the vertical plane passing through the reference rod 27 , cutting across it as shown . the resulting path of a ball struck under these conditions would veer considerably to the left of the desired direction . the reference rod 27 can conceivably be of almost any material . preferably , it is formed from straightened steel rod approximately 0 . 093 &# 34 ; to 0 . 125 &# 34 ; inches in diameter . the length is preferably in the neighborhood of 18 &# 34 ; to 24 &# 34 ; inches . a convenient handle for manipulating the reference rod , particularly when it is inserted and removed from storage position in the shaft , is provided by a hollow rivet 31 selected so that the inside diameter of the rivet can form a press fit with the reference rod 27 . referring to fig5 the grip 23 of the usual golf club is of a rubber - like material extending across the end 32 of the shaft 22 . the standard grip is already provided with a central opening at the end 32 , and this is utilized by the arrangement shown in fig5 for retaining the reference rod 27 in position . the outside diameter of the shank 33 of the rivet is selected for a gentle push fit in this standard end opening in the grip . the resulting friction adequately retains the reference rod in storage position when the club is inverted for insertion into the golf bag . in fig6 a screw 34 is affixed by either welding or adhesive to the end of the reference rod 27 , with the threads of the screw providing an increased interengagement with the material of the grip at the end of the shaft . in fig7 a further modification is illustrated in which a device similar in shape to a shirt stud , indicated at 35 , is secured to the end of the rod 27 , with the enlargement 36 providing a more positive retention of the rod in the shank of the club . in the arrangements shown in fig5 and 7 , the rod can be withdrawn from storage position by slipping the fingernails or a blade under the head of the rivet , and simply pulling the rod out of engagement with the grip material . in fig6 the rod should be removed with a screwdriver or a a coin adapted to engage the slot of the screw . it is obvious that a reference rod retained solely at its upper extremity would rattle on impact of the club head with the ball , which is clearly undesireable . in fig3 this is prevented by the addition of a plug 37 pushed down into the shank 22 to form a stop to a collection of loose material indicated at 38 which the inner end of the rod is forced into on insertion into the shank of the club . the loose material may be a mat of fiberglass , a handful of loose sand , or practically anything that can be penetrated by the rod 27 . it is only necessary that the mass of material 38 be in the position illustrated in fig3 when the club is generally vertical . in fig4 a modified form of anti - rattle system involves a plastic device 39 pressed down into the tapered shaft 27 until its progress is impeded at the annular offset 40 , where it can be retained either by the effect of a press fit , or by adhesive . the device 39 preferably has a conical lower end with a slot or hole capable of receiving the reference rod 27 , and the interengagement shown in fig4 obviously prevents the rod from rattling against the inside of the shaft as the ball is struck .
a thin rod is removeably received in the hollow shaft of a golf putter . when the rod is removed and placed on the ground , it interacts with reference indicia on the top of the club head to indicate deviation or alignment of the club position and movement with respect to a proposed direction of ball travel .