Transverse roof beams that span the distance from the center posts of a vernacular house with a thatched roof to the *kawabashira 側柱 or *geyabashira 下屋柱 along the sides of the building. The beams are large in cross-section and straight for most of their length but bend sharply downward at the peripheral zone of the building *geya 下屋. The shape of the beam is thought to look like an adze *chōna 釿, hence the name chōnabari. The main purlin *jōyageta 上屋桁 is supported by the chōnabari, allowing the mainframe posts *jōyabashira 上屋柱 to be dispensed with and avoiding the need for inconvenient supports. This vertical economy, however, requires a doubling of the horizontal plane because the chōnabari do not support the *sasu 叉首 directly. Instead jōyageta and other longitudinal members that lie on the chōnabari support the main transverse beam *jōyabari 上屋梁. The carpenters *daiku 大工 of the period made imaginative use of the twisted trunks growing on the steep mountain slopes near the structure, allowing roof loads to be transferred to the lower geyabashira and the elimination of the jōyabashira. Chōnabari were usually disposed symmetrically in the parts of the building where they were used. They became a popular stylistic feature doubtless because of their impressive appearance. Also referred to as teppō 鉄砲 (gun), because of a perceived resemblance to a gun.
