Shihou-ari-tsugi

Shihou-ari-tsugi wooden joinery technique:

- Shihou means "four directions" or quadrants
- Ari means "existing" or being placed 
- Tsugi refers to the joining method

To form this joint:

- The ends of two wooden pieces meeting at 90 degrees are prepared, usually with miter cuts.

- Intricate interlocking wedge or spline shapes are cut into each piece, following the grain in four symmetrical sections.

- This divides each end into four matchings "quadrants".

- When joined, the corresponding quadrant shapes in each piece fit together securely.

Traditionally used in Japanese carpentry, this joint transfers load stresses evenly in any direction by engaging all four-grain quadrants.

Even without glue or fasteners, the synchronized interlocking sections strongly bind the pieces at the corner intersection.

The shihou-ari-tsugi demonstrates the exceptional mastery of traditional Japanese woodwork craft and leveraging wood's natural structural properties for joinery. It remains applicable for demanding architectural woodwork today.