accessible for Customs inspection. 3. Should any empty spaces be formed by the different layers of the sides, floor and roof of the means of transport, the inside surface shall be firmly fixed, solid unbroken and incapable of being dismantled without leaving obvious traces. 4. Openings made in the floor for technical purpose, such as lubrication, maintenance and filing of the sand-box, shall be allowed only on condition that they are fitted with a cover capable of being fixed in such a way as to render the loading compartment inaccessible from the outside. 5. Doors and all other closing systems of means of transport shall be fitted with a device which shall permit simple and effective Customs sealing. This device shall either be secured by at least two bolts, riveted or welded to the nuts on the inside. 6. Hinges shall be so made and fitted that doors and other closing systems cannot be lifted off the hinge-pins, once shut; the screws, bolts, hinge-pins and other fasteners shall be welded to the outer parts of the hinges. Theses requirements shall be waived, however, where the doors and other closing systems have a locking device inaccessible from the outside which, once it is applied, prevents the doors from being lifted off the hnge-pins. 7. Doors shall be so constructed as to cover all interstices and ensure complete and effective closure. 8. The means of transport shall be provided with a satisfactory device for protecting the Customs seal, or shall be so constructed that the Customs seal is adequately protected. 9. The foregoing conditions shall also apply to insulated vehicles, refrigerator vehicles, tank vehicles and furniture vehicles in so far as they are not incompatible fulfil in accordance with their use.