ishi-otoshi 石落

Also termed ishi otoshimado 石落窓. Stone drop, or stone drop window. A castle installation built into the keep *tenshu 天守, towers *yagura 櫓, walls hei 塀, and gates *mon 門, that enables the defenders of a castle to observe an enemy climbing the stone wall and to counterattack by dropping stones, and other objects, or to shoot arrows or fire guns. Typically, it is a timber frame construction built out slightly over the plane of the stone wall, usually with a floor covered by a wooden lid that can be removed when necessary. The opening is 0.26 m, eight Japanese inches, sun. The width had to be large enough for the stones to pass through and to small for the enemy to sneak into the castle if the stones missed their mark. Some ishi otoshi projected out in narrow skirts located at strategic points around the castle wall (Right Corridor, Himejijō 姫路城); others projected out all around the perimeter of the structure (the Keep, Kumamotojō 熊本城 and the Keep, Hagijō 萩城); some also projected out from the windows, (the Keep, Hirosakijō 弘前城). Similar in form and function to the machicolations in the European castle tradition.