robuta 炉蓋

A wooden lid about 1.8 cm thick used to cover the fixed-hearth *rodan 炉壇 in a tea ceremony room *chashitsu 茶室, usually from May to October. It's called jotan 助炭 for a protection of the sunken hearth *ro 炉. The portable brazier *furo 風炉, replaces the fixed-hearth during this time. Changing from a portable brazier back to the fixed-hearth is called robiraki 炉開き (opening the fixed-hearth). Furthermore, the fixed-hearth, if not in constant use, is usually covered during the winter months. It's called settō 雪洞.
The lid is a simple board about 2 cm thick made of paulownia, Japanese cedar, pine, zelkova or other wood. On the underside of the lid, two lengths of wood slightly more than 1.5 cm square are attached somewhat inside the outer dimensions of the top so that they will fit snugly into the fixed-hearth.
The lid is level with the surface of the matting *tatami 畳. A small round hole 1.5 cm in diameter is cut in the exact center. If the fixed-hearth is located within the middle board *naka-ita 中板, the lid is made of the same kind of wood as the middle board.