Isukatsugi

Known in English as diagonal joinery or baton reinforcements, isukatsugi is a traditional Japanese woodworking technique used to rigidly strengthen structural intersections and corners.

 It utilizes thin strips of wood cut on the diagonal grain and wedged tightly inside vertical and horizontal framing members with their fibers running counter to the surrounding grain. Primarily employed as an internal bracing system for timber-framed buildings, isukatsugi was widely adopted in constructions like shoji walls, tatami mat foundations, and roof trusses to distribute stress across the wood grain. 

By reinforcing vulnerable connections and junctions with these narrow cross-grain reinforcements, master carpenters were able to fortify entire frameworks against cracking and collapse and still allow for seasonal movement without loosening the joints. The rigidity imparted by the opposing diagonal wood fibers has helped maintain the structural integrity of centuries-old Japanese temples, shrines, and homes. Even today, isukatsugi's discreet but mighty diagonal joinery remains an elegant and enduring solution for reinforcing wooden structures where durability matters most.