PURPOSE: To prevent an adverse effect on a ball driven at the tip on the top side of a frame stretch section and reduce the expansion load of guts caused by a shock when the ball is driven by providing auxiliary frames for holding vertical guts, and movably suspending them at one end.

CONSTITUTION: Both end sections 3a and 3a of auxiliary frames 3 and 3 are inserted into through holes 4 penetrated on a frame stretch section 2 and slide- coupled and movably held in the longitudinal direction Y-Y by bearings 5, and vertical guts G1 are indirectly stretched between auxiliary frames 3 and 3. The shock force of a ball is propagated to a frame via vertical and horizontal guts G1 and G2, and particularly auxiliary frames 3 and 3 are displaced in the inward direction by the component force Fy in the longitudinal direction Y-Y on the X-Y plane and also displaced in the outward direction by the component force Fz in the driving direction Z-Z on the Y-Z plane. The expansion load of guts G1 and G2 caused by the shock when the ball is driven is decreased, and guts G1 and G2 made of high-elastic modulus fibers can be used.