Hibukuro (火袋)

The blowout above the hashiriniwa allows hot air and (when wood was still used to make fire) smoke from cooking to exit the house. It also is a measure against the spreading of a fire by containing the flames long enough to give firefighters a chance to extinguish them before the adjacent houses begin burning. Because of the intricate design, it is said that a carpenter's real skills show in the way he made the hibukuro.