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Long ago, shipbuilders used iron nails and bolts because iron was easy to find. They soon learned the disadvantages of using this metal on a boat! Iron quickly rusts and decays, especially near the salty ocean. They switched to using brass, which lasts longer.

Shipbuilders also had to consider how to make a wooden boat watertight. The planks on the bottom of the boat had to be joined very closely together so water did not seep in. Just like how plumbers use a paste to keep your kitchen sink from leaking, shipbuilders applied a paste called "caulk" between the planks. They first used seashells ground into a fine powder. This caulk cracked easily and fell into the sea. They tried burning the shells, but this did not make the caulk any better. At last, shipbuilders thought to try thin pieces of copper metal, and it worked.