The method used to attach a purlin *jōyageta 上屋桁 and transverse beams *jōyabari 上屋梁 to the top of a pillar in a farmhouse or merchant's dwelling. A tenon, cut from the pillar top, and a corresponding mortise, cut into the purlin, are joined together. Then the transverse beam is attached to the purlin by means of a cogged joint *watariago 渡腮 or a dovetail joint kabuto arikake 兜蟻掛 (see *arikake 蟻掛). This arrangement has the advantage of providing support for the beam-end whether there is a post directly below it or not, and therefore allows posts to be omitted with relative freedom and without disturbing the regular spacing of roof members. Kyōro construction contrasts with the *oriokigumi 折置組 arrangement in which the position of beams and plates are reversed. Orioki appears to be the older arrangement, with the kyōro system emerging later but then becoming the predominant system in vernacular houses *minka 民家 during the Edo period.
