棟
とう · tou · JLPT N3 · noun
roof
🏠🪵 木 wood + 東 tou (east): the wooden roof beam that reads tou
東 (east) is also read とう, so it gives 棟 its sound, and 木 marks it as timber. The ridge beam is the highest timber in a roof. 棟 also counts buildings, as in 二棟 (two buildings).