Sumigi (隅木) – one of the sloped corner beams on a hipped roof — also known as a hip rafter. Roofing taruki is precut to meet the sumigi at predetermined intervals – usually “shaku-gosun” which is roughly 455 millimeters, but also “shaku” (about 303 millimeters) if taruki is in the 45 millimeter square range. However, the roof slope can also change the taruki pitch regardless of its dimensions, as a roof closer to level will require closer intervals.
(Roofing taruki is the equivalent of a rafter, and is used to mean both common rafters as well as the hip jacks.)
Sumigi is the base beam that supports adjacent rafters and joists and is also typically the surface on which plywood or roofing tiles will sit. It therefore must be cut with the proper angles so as to create the necessary surface for two sides of the roof that will form a joint at this point.