Rather than the more common through tenon joint where wedges are pounded through square holes in the tenon, this joint uses wedges in a creative way to make a very secure wooden joint option.
This through tenon has two 6″ angled cuts starting at the tip of the tenon and running down towards the post. The wedges are pounded into these cuts once the tenon is installed in the mortise. The mortise in the receiving beam is cut with a wider angle near the top edge to allow the tenon room to open when the wedges are driven in using a timber framing mallet.
This process essentially creates a dovetail joint, securing the tenon in the mortise. After the wedges are in place, the excess wedge material is sawn off flush with the rest of the tenon.
Tim took this photo during a Japanese timber framing course taught by Dale Brotherton and Robert Laporte. For more information, visit their websites at www.japanesecarpentry.com and www.econest.com