Each one by hand is worked together to form a planar blade by hammered iron (bare metal) to fire the shape of a plane.
It is trained by traditional techniques that have been inherited from ancient Japanese swordsmiths.
Hagane is made of hard, sticky blue paper No. 1, and the base metal is soft and brittle chain wrought iron (cauldron).
The sharpness of the planes is greatly affected by sharpening.
Unlike the ultra-soft iron made in todays iron mills, many impurities and fragile kilns are extremely soft, making it easy to sharpen and have a sharp blade.