PURPOSE: To enable effective pressing and extrusion of a short bent tube by aranging rosary-like chain body made of alternately adjoining cylindrical bodies and spherical bodies having penetrated holes positioning the center of spherical bodies at intersections of axial lines of cylindrical bodies in a curved hollow.

CONSTITUTION: When a rosary-like chain body consisting of alternately adjoining cylindrical bodies 2, 4 and spherical bodies 3, 5 having penetrated holes 9 is in a curved hollow, the center of spherical body 3 is positioned at intersection B of axial lines A, A' of the cylinrical bodies 2, 4 on both sides of the spherical body 3. The chain body is allowed to bend freely, and individual component is connected by a tie cord that passes through the holes 9. However, as there is considerable freedom, each component can rotate more than necessary. When the body is placed in a curved hollow as mentioned above, excessive inclination to the axial line of the bent material tube is restrained.