Built in 1858, the hot shot furnace was intended to heat cannonballs for 32-pounder cannons planned for but never installed at Fort Knox, where the heated shot would have been fired at enemy ships to set them ablaze. The Rodman cannons later installed in Battery B fired much larger cannonballs whose size, rather than heat, could damage the fireproof ironclads that had largely replaced wooden-hulled ships by the 1860's. Although the furnace was never fired up, it remains an important feature of early cannon technology. In operation, soldiers would have built a probably coal fire in the side firebox, heated the interior, loaded cold cannonballs into one end, and let them roll down sloping rails until the first balls rested over the firebox for about 30 minutes until red hot. They then would have removed the heated balls with iron forks, scraped off scale with a rasp, and carried them in iron and wood ladles to nearby cannons as the next set rolled into place.