Abstract: Child-proof turn-lock closure of plastic material for threaded mouths on containers, particularly on bottles, with a screw cap closure on which an outside cap is clamped with axial play, both of which caps are provided with projections or projections and grooves which, within the axial play, can engage in each other, those sides of the projections or grooves which touch each other when the cap is screwed down being made as carriers, while those sides of the projections or grooves which touch each other when the cap is screwed off act as wedges, and in such a way that, when being screwed down, the screw cap is carried by the outside cap but when being screwed off this only happens when an axial pressure is exerted on the outside cap and directed against the container, wherein recesses are provided in the face of the screw cap, which are covered by a gas- and liquid-impermeable inlay cover. The closure is particularly suitable for bottles containing hypochlorite.