The shape of the section used for heating porcelain flasks full of sake is generally rectangular, but the openings in the water reservoir in the upper section of the unit have round openings to facilitate the insertion of sake flasks for warming.
湯を貯め徳利を湯煎する部分の形状は概ね直方体で、上部に給水口を兼ね徳利を挿し入れる丸い穴が開けられている。