stay bar 1 as shown in fig2 in the meantime the tubular elastic body 30 is preferably fabricated in various forms in size according to change in diameter of the stay bar 1 but since the tubular elastic body 30 has an elasticity naturally there is no reason to produce the tubular elastic body 30 in various sizes certainly because there is no problem to use it even if diameter of the stay bar 1 is a little big or small further since the standard and diameter of the stay bar 1 are substantially the same only one basic type of the tubular elastic body 30 can be used without causing any problems as described above after the tubular elastic body 30 is inserted into the stay bar 1 a hole is formed on the stay bar 11 through a hole 32 using a hand drill the diameter of the hole does not cause any hindrance in intensity of the stay bar 1 in this case if the end portion of a rotation preventive screw 16 may be inserted into the hole the diameter of the hole can be acceptable here the tubular elastic body 30 can be assembled with the stay bar 1 after a hole has been formed on the stay bar 1 next after a semicircle upper clamp 10 is positioned at the upper portion of the tubular elastic.