Hari is a flat length of wood, like a thin beam, used to connect pillars and larger beams in traditional Japanese architecture. Generally, the direction of a hari is the same as the depth of a building, and the unit is one 'ken'. One ken is about 18.182m long.

Also, in construction using materials other than wood, there are parts corresponding to hari that play an important role.

The history of hari dates back very many years. In ancient buildings still standing today, you can see naked haris taking advantage of the natural curves of the wood. Using natural wood without processing leads to stronger structures. Hari has an artistic attraction, too, for modern people; some houses have a roof featuring hari which is not for strength but for design.