When we think back to the age of discovery, the age of sail, or the age of pirates, we automatically invoke images of square-rigged wooden sailboats. Columbus's Niña, Pinta, and Santa Maria are perhaps the best-known ships of the genre, but there were thousands of ships like these transporting people and goods around the world. These boats were made in shipyards by craftsmen, who learned their trade through apprenticeship and experience. But in mindset they were engineers, designing and building custom vessels using a common basic architecture. That architecture dominated shipbuilding until steel refined using the Bessemer Process completely reconceptualized the design and construction of ships in the late nineteenth century. The architecture was surprisingly straightforward and consisted of four parts. First there was the main spine of the ship, known as the keel, which ran down the center of the vessel's bottommost point. This was a stout square timber carved from a single log, or joined together from multiple logs, depending on the length of the ship. At the front of the keel, multiple pieces of wood were joined together to make the curving stem extending up and forward from the keel. At the back, a sternpost joined the keel and rose vertically. Second, attached to the keel was a set of sturdy ribs or frames made from multiple pieces of wood, called futtocks, joined together. The ribs attached to the keel with the help of pieces called floors. Ribs determined the shape of the outer hull. Third, the top deck and any interior decks were formed with horizontal beams attached to the ribs. Finally, the outer surface of the hull, as well as the deck flooring, was made of one or more layers of planking. The planks attached to the ribs or beams with trunnels— pieces of wood dowel seated with wedges driven into their ends. Rope soaked in tar would be driven between planks to seal the gaps, and then sealed over with more tar. Once the hull was complete, the masts could be seated and then their sails and rigging added. This basic wooden architecture— an engineered solution to the wooden boat problem-served humankind well for several centuries.