Union navy blockades isolated the Confederacy from world markets, creating shortages of almost every kind of commodity. Southerners could barely find a piece of unused paper by the time the war ended. As a result, every available scrap with sufficient writing space was pressed into service, creating a collecting category called 'adversity covers'. Turned covers were one of the first signs of the growing paper shortage. Envelopes from previous correspondence were carefully turned inside out, regummed, and used again. Sometimes a single envelope was reused three or four times before the sheer weakness of its folds forced its retirement. The previous stamp was either removed or covered with a new one. People stripped books of their flyleaves and title pages for letter paper and material for homemade envelopes. Tax receipts, wrapping paper, election ballots, bank checks, insurance blanks, military requisitions, religious tracts, accounting forms, and music sheets were just some of the alternative sources.