PURPOSE: To generate a simple connected state between two structural parts without any axial play by forming a projection in a tubular shape, fitting the other component, and trimming the fitted structure portion of the projection turned inside out and bringing this into contact with the structure portion.

CONSTITUTION: To obtain a connection, a pressure stumper 8 is moved into the hole portion of a tubular projection 5, its advancing is continued to enter and the projection 5 is thereby expanded, and when the projection 5 reaches the region of a ring groove 12, the projection is folded along a groove bottom portion 13 and as a result, the projection 5 is provided with a sliding ability in a taking-out surface 14, and the inner side face of a support pot 3 is supported by holding the tail end of the projection 5. Then, the pressure stumper 18 is moved again to the outside. Thus, the tail end of the projection 5 is pulled in on the basis of the memory function of a selected plastic material for an adapter ring 2 or the projection 5. Therefore, the necessity of turning inside out is eliminated, and a connected state is secured between the support pot 3 and the adapter ring 2.