Built as a fortress, the Japanese castle was designed to be defended by a relatively small number of warriors. Thus, small openings (called sama) were built in the walls, allowing defenders to shoot safely.
Originally built for archers, the sama were later designed with a different shape, for guns. Those made for archers (ya-zama, from ya, “arrow") were rectangular, while those made for guns (teppō-zama, from teppō, “gun") were circular or triangular.
Yesterday’s Japan Photo: