3D model: Miyajima-tsugi by thejoinery on Sketchfab
Assembly insights
Watari Ago's stepped tenon and haunch combination prevents twisting under dynamic loads, making it a hallmark of shrine galleries exposed to the elements. The beam passes through the column with offset shoulders that resist racking in multiple directions—a refinement of the basic Nuki joint for applications where wind and foot traffic create complex stresses.
Historical context
Watari Ago (passing jaw) evolved for verandas, covered walkways, and bridge construction where horizontal members must thread through vertical posts while maintaining anti-racking strength. The stepped profile distributes load across haunches rather than relying on friction alone. Miyadaiku use it alongside Nuki and other shiguchi in shrine and temple galleries that remain open to weather on one or more sides.
Construction steps
- Lay out the mortise on the column; mark the stepped shoulder positions and through-passage.
- Bore or chisel the primary mortise, then cut the haunch recesses for the offset shoulders.
- Shape the beam tenon with matching steps and haunches on the kiguchi kanna or with chisels.
- Test-fit; the joint should resist twist when the beam is fully seated.
- Secure with wedges or pins if the design requires tension across the connection.
Where to see this joint in Japan
- Itsukushima Shrine — Hiroshima — veranda and gallery framing
- Temple covered walkways — Kyoto and Nara — open-sided gallery structures
Variations
Shoulder depth and step count vary with timber size and expected load. Some versions combine Watari Ago with visible pegs (komisen); others rely on friction fit alone. Related joints include Nuki (simple through beam) and Tsuki Uchi Wa (blind mortise).
Applications
- Temple verandas
- Covered walkways
- Bridges
Tools required
- Ryoba saw
- Oire-nomi chisels
- Kiguchi kanna