Hanasen

Hanasen, known in English as projecting tenon joints, is a wood joining method used in historical Japanese architecture. With hanasen joinery, lengthy tapered tenons are cut into the ends of each beam that will connect to an upright post. These tenons project outward from the beam ends, their grain running parallel. Corresponding mortises are then cut into the posts to receive the tenons. When fitted together, the longitudinal grain of each tenon inserts into the vertical grain of the matching mortise hole. Called hanasen due to the "projecting hands" shape of the tenons, the cross-grained connection creates tremendous structural rigidity. Yet it also permits a degree of flexibility as the beams can subtly move with any wood expansion or contraction. The durable hanasen joint allowed frameworks such as those found in temples and timber bridges to withstand immense structural loads for centuries.