The correct answer is “They were used to make ammunition and explosives”
After the Japanese attack on Pearl Harbor, US joined the WWII. Many commodities such as rubber and cloth were precious and the government encouraged American citizens to contribute across the country and give rubber, unused clothes, nylon and silk stockings, and any leftover fat to make jeep tires, cleaning rags, parachutes, and explosives.
Metal was a vital material to make tanks and ammunition. Because of that, people donated pans, old tractors, iron fences, trolley tracks, anything that could be transformed into ammunition, tanks, and explosives. This actually didn’t help a lot but brought citizens together as a patriotic unity.