Shachisen

Shachisen, known in English as staggered multiple tenon joints, is a intricate wood joining method used in Japanese architecture. With shachisen joinery, several short tenons are cut sequentially along the length of a beam end, with each subsequent tenon staggered slightly from the last. Corresponding interrupted mortises are then cut along the facing post to receive the staggered tenons. When fitted together, the transverse grain of each tenon is oriented perpendicularly to the longitudinal grain of the beam it joins, as well as the vertical grain of the post. Called shachisen due to this "staggered arrangement", the cross-grained connection provides tremendous structural integrity while permitting expansion/contraction movement. Historic structures like castle gates and multi-level houses incorporated shachisen mastery, enduring immense overhead loading through layered cross-grain reinforcement for centuries.