Regarding small castles, a simple building was made to store food and weapons and fences, moats and mud walls for defence were made by using natural terrain, whereas medium-size castles had Kuruwa (walls of a castle), a main compound on one peak and a secondary compound on another peak, and residential facilities that made it possible to hold out against a long-lasting siege.
小城の場合は、山の頂上に簡単な建物を造り、食料、武具を保管するだけで、後は自然の地形を利用して、適宜、山の各所に柵、堀、土塀を設けるといった程度であるが、中規模の城となると峰々に本丸、二の丸といった曲輪を造り、居住用の施設も備え、長期の籠城に耐えられるようにした。