A Sashigane is a traditional Japanese carpenter's square. It's an L-shaped tool used for drawing layouts, measuring lengths, and calculating angles. This tool is essential in Japanese woodworking, especially in constructing houses and complex buildings like temples.

The Sashigane has measurements on both sides, with a standard scale on the front and a special scale based on the square root of 2, called "kakume" on the back. There's also a circle circumference scale known as "marume".

Kakume scale: A scale graduated in √2 times the actual length for measuring the largest square possible to be cut out from a circular material.

When the Kakume scale indicates 30 as the diameter of circular material, the largest possible size of a square to be cut out from it is 30 cm long.

Marume scale: A scale graduated in 1/π times the actual length scale for measuring the circumference of a circular material.

When the Marume scale indicates 90 as the diameter, the size of the circumference is 90 cm long.

A flexible Sashigane can be incredibly useful for several reasons:

Versatility: It allows you to measure and mark angles on curved or irregular surfaces, which is often challenging with a rigid square.

Precision: Flexibility can help in achieving more accurate measurements in tight or awkward spaces where a rigid tool might not fit properly.

Durability: A flexible Sashigane is less likely to break or get damaged if accidentally bent or dropped.

• Maximum length: 500 mm
• Maximum measurement of a square within a circle (Kakume): 300 x 300 mm
• Maximum circumference of a circle (Marume): 100 cm (Diameter 31.831 cm)
• Squareness of scale side face: Less than 0.5 mm per 500 mm
• Length tolerance: 500 mm ± 0.2 mm
• Material: Stainless steel