member 98 has inwardly bent end bars 101 transversely extending therefrom and connected to the pivot pin 100 leg 70 of the yoke 68 is formed with a slot or recess 106 which is of a substantially rectangular shape hook 102 has a substantially c shaped configuration and is inserted into recess 106 upon pivoting of locking member 98 towards leg 70 manipulating lever 104 is bent at right angles to an elongated center portion 108 of its leg the hook 102 and manipulating lever 104 are bent or curved in opposite direction in respect to the elongated center portion 108 of the locking member so that by manipulating the lever 104 to pivot locking member 98 about pivot pin 100 the hook 102 is engaged in or disengaged from the slot 106 thus locking or unlocking clamp 80 onto the pole inserted in the clamping device 60 in fig3 the closed position of clamp 80 is shown in solid line while its open position is shown in dotted line on the outer side of leg 70 of the yoke member 68 of the clamping device there is provided a screw holder 110 also seen in fig4 screw holder 110 is somewhat resilient typically of rubber and is secured by any suitable adhesive or other means to the outer surface of leg 70 of the yoke member.