This tearoom within the same building as the Kaiin-seki Tearoom but situated on the eastern side of the mizuya (tea ceremony preparation area) is named "Masudoko-seki" (lit. masu alcove tearoom) as it has an alcove with a board floor at the same level as the tatami mats which resembles a regular square measuring container known as a "masu."
閑隠席と同じ建物内、水屋を隔てて東側にある茶室で、枡形（正方形）の踏込床があるため桝床席と呼ばれる。