PURPOSE: To improve the molding efficiency and to reduce the weight thus to reduce the unit production cost by making a through-hole at the crossing section between the fold guide sections at the opposite ends of traverse guide groove while providing a support member between corresponding inner faces of endboards to be applied onto the opposite ends of tubular member.

CONSTITUTION: A traverse guide groove 2 integrally formed with a tubular body 1 is made of folded guide sections 3, 3 at the opposite ends in axial direction and guide grooves 4, 4 having spiral shape between said guide sections 3, 3 while crossing at the crossing section 5. In order to make one guide groove 4a deeper than the thickness of tubular wall 1a at said crossing section 5, thin through-hole is penetrated through the tubular wall 1a while wide through-hole penetrating through the tubular wall 1a at the portion striding over the crossing point 5 is employed for the other groove 4b. A pair of metal support members 21, 21 are fitted between the corresponding inner faces of the endboards 11, 11 then fastened through many screws 31 from the outer face of tubular body 1 thereafter endboards 11, 11 are applied to be assembled through fastening screw 32. In such a manner, easily moldable tubular body is molded thin while through-hole is employed at the crossing section requiring deep groove and a support member is provided to improve the strength.