B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
B65D27/00—Envelopes or like essentially-rectangular flexible containers for postal or other purposes having no structural provision for thickness of contents
B65D27/12—Closures
B65D27/30—Closures with special means for indicating unauthorised opening