The traditional sashigane square is so important to Japan's carpentry tradition that it is used symbolically in rituals and festivals, as well as on site and in the shop.
Supremely useful in countless ways, the sashigane features a number of key differences wen compared to Western squares. Both arms are flush with each other and flexible, meaning it can be laid on a work surface and marked against.
The entire square is profiled, with the edges of each arm thinner than their middles. This is a design feature that allows traditional ink marking tools to be used with the sashigane without bleeding along the tool and smudging the mark.
The square is thickest at it's very corner, allowing it to be adjusted for square if its befallen by a misadventure.
Finally, and most importantly, only one side of this sashigane displays centimetre markings. The reverse shows three seperate scales. The long arm features a mortice gauge counting up from the end of the arm, meaning it can be used to measure the depth of a mortice or trench. It's short arm shows a pi-based scale, allowing the carpenter to assess the largest possible square section that can be cut from single long. Finally, the long arm displays a pythagorean scale, used in the measure and calculation of roof pitches and angles.
This phenomenal tool is a wonderful example of a simple task executed with perfect refinement.