10. The flanges (filler caps), drain cocks and manholes of tank wagons shall be so conducted as to allow simple and effective Customs sealing. 11. Folding or collapsible containers are subject to the same conditions as non-folding or noncollapsible containers, provided that the locking device enabling them to be folded or collapsed allow Customs sealing and that no part of such container can be moved without breaking the seals.