Method for manufacturing an assembly of two ringed sheaths (1,2) ready to be used to make a single ringed sheath around for example a bundle of electric cables (13), wherein two smooth-walled tubes are simultaneously extruded using a single extruder fitted with two extrusion nozzles, the two smooth-walled tubes are simultaneously molded into two ringed wall tubes using a molder equipped with molds each fitted with two ringed profiles extending in parallel in a longitudinal direction and being paired along one and the same parting line. According to the invention, during molding, material bridges (33) and empty spaces (35) are created between first tube rings (41) and second tube rings (42), by opening or closing respectively, between the two ringed profiles, material runs formed in the parting line of two paired molds, a longitudinal strip (28) of ringed tube wall is cut out and removed, using cutting means and the two ringed tubes connected to each other by the material bridges (33) formed between the rings are cut to a desired length, using severing means.