A fitting is inserted into an opening in a wall. The fitting includes a ring portion where it extends through the opening. It also includes one or two end portions that extend axially outwardly from the ring portion. The ring portion has an inside diameter that is smaller than the inside diameters of the end portion or portions. The fitting is positioned within the wall openings. Then, an expansion tool is moved through the interior of fitting for the purpose of expanding the ring portion. The ring portion is expanded to such an extent that it makes a tight fit with the opening. Also, the degree of expansion may result in a cold working of the wall material surrounding the opening. The expansion tooling only expands the ring portion and does not exert a substantial expanding force on the end portions.