Hull Fissures Fuel Lines Ductwork Ammo Cases 
Answer: Ammo Cases
At the beginning of the 20th century, adhesive tapes in their modern form were just starting to appear on the market. Early tapes were typically strips of cloth with adhesive on one side as well as primitive early forms of electrical and medical tape. Throughout the 1920s and 30s, many of the modern tapes like paper masking tape and cellophane gift wrapping tape appeared.
What do-it-yourselfer’s and all those with a little bit of MacGyver in their hearts will likely consider the pinnacle of tape inventions, the durable and ever useful duct tape, didn’t appear until 1943, however. The silver tape we now refer to as duct tape began life quite far from heating and cooling ducts (and, for that matter, had a very short run as a heating and cooling duct tape to begin with). During World War II, a worker in an ordinance factory, Vesta Stoudt, wrote to President Franklin D. Roosevelt with her concerns over the seals on the ammunition cases. She was worried that the amount of time it took to break and remove the seal from the cases was costing U.S. soldiers precious time in battle and proposed that the ammo cases be sealed with an easy to tear fabric tape.
Roosevelt passed the idea on to the War Production Board, Johnson & Johnson was tasked with creating a waterproof plastic backed tape that was easy to tear, and an olive drab version of the now ubiquitous silver tape was put into use by U.S. military units around the globe. Soldiers found all sorts of uses for the sturdy and easy to apply tape, and when they returned home from the war, Johnson & Johnson began selling duct tape at hardware stores across the country.