Methods and apparatuses for creating blow-molded components are disclosed. More particularly, the present invention concerns methods and apparatuses for creating double-wall blow-molded components with one or more protuberances not abutting a parting line of a mold. Generally, the protuberances are created by a method comprising the steps of blowing blow-molding material against a molding surface with a cavity of a predetermined shape, so that the blow-molding material enters the cavity at a first end, and urging the blow-molding back toward the first end of the cavity by moving a piston of a predetermined shape. The invention also concerns apparatuses to employ such methods, and the resulting blow-molded objects.