One of several arrangements for positioning the fire-box *ro 炉 or fixed hearth in a small tea ceremony room *chashitsu 茶室. With the positioning called *hongatte 本勝手, sumiro is cut into the front left corner at the narrow end of the host's mat *temae datami 点前畳. In the reverse position *gyakugatte 逆勝手, sumiro is cut into the front right corner at the narrow end. In the latter position, the fire-box is also known as the *mukōgiri 向切 type.
According to the *Nanbōroku 南方録, written by Nanbō Sōkei 南方宗啓 (?-1624?), Tachibana Sōyū 立花宗有 stated that in consultation with Sen no Rikyū 千利休 (1522-91), they devised a 2-mat room, nijō chashitsu 二畳茶室. Rikyū stated that a 42 cm square fire-box could be made by measuring the distance from the *daisu 台子 to the opposite corner and then cutting it there. Chadenshū 茶伝集 (1847) by Sōmu 宗務 states that the corner firebox should be installed on the kitchen side, with a 5-cm-wide board inserted between it and the wall. Without the board it was difficult to grasp the handle of the water ladle *hishaku 柄杓, and the wall might be damaged by the heat from the fire-box. Usually, at least a 4-cm-wide straight grained board is inserted between the wall and a fixed-hearth. During Sen no Rikyū's lifetime, the expressions migimuki 右向, meaning to face right, and hidarimuki 左向, to face left, were commonly used. Sumiro is a more recent usage. See *iriro 入炉.
Examples: Myōki'an Tai'an 妙喜庵待庵, Kyoto; and Kanden'an 菅田庵, Shimane Prefecture.