hara 腹

Lit. "belly." The concave underside of a curved beam, for example, a curved transverse beam *koyabari 小屋梁. The upper side is convex and is called *se 背. When a beam is cut on the upper side, the uncut or unshaped under side is called hara. Hara can also mean both sides, ryōwaki 両脇 of a board. If the entire beam is rounded, the whole beam is referred to as hara.