The kuruwa that plays the most important part in defense is the honmaru (hon-kuruwa/main enclosure), and in addition to it, mostly ninomaru (second bailey) and sannomaru were built.
防御の中心となる曲輪は本丸（＝本曲輪・主郭）であり、他に二の丸・三の丸が設けられることが多かった。