Fort. An Ainu アイヌ term for a fortification surrounded by a stockade fence or palisade *saku 柵. Many had earthen embankments *doi 土居 and dry moats *karabori 空堀. Chashi were built in strategic positions yōgaichi 要害地, on mountain tops, and close to lakes, rivers, the sea, and on islands. Remains of chashi have been found in approximately 1000 sites in Hokkaidō 北海道 as well as several dozen sites in Tōhoku 東北 and Sakhalin. Many are irregularly shaped, following the lie of the land, but some are square, round, or a combination of these shapes. Square chashi are most common in northern and eastern Hokkaidō, and round ones in western and southern Hokkadō. Some chashi consist of a single fort, but many combine two or three structures, and chashi with as many as 7 or 8 forts have been found. Chashi excavated so far have dry moats between 2 m and 8 m wide, with embankments a few meters high on the inner bank of the moat. The inner measurements (inside the moat) vary from 14 m by 40 m, to 50 m by 110 m. Examples include Koshiyamain コシヤマイン in Hakodate 函館 City, Setana 瀬棚 in southwestern Hokkaidō and Ōkawa 大川 in Yoichi 余市, near Sapporo 札幌. The term chashi survives in Hokkaidō place names, written 茶志, where the Japanese characters are used phonetically. Some scholars have also proposed that the origin of the term is not the Ainu language but the Korean word chat, which means fortress.