腰開互の目 (Koshihiraki Gunome)

What is Koshihiraki Gunome in Japanese Katana terminology?

Koshihiraki Gunome refers to a type of blade pattern (Hamon) in Japanese swords. It is a variation of ""互の目"" (Gunome), where the 'heads' of the 'nails' (gunome) are aligned in a 'checkerboard' style. In ""腰開互の目"", the 'heads' of the 'nails' are particularly spaced apart, creating a pattern that resembles a mountain range.

In many cases, small irregular patterns are mixed into the mountain-like gunome, creating a complex blade pattern (Hamon). This pattern is often seen in swords from the Kamakura period and is considered to be one of the characteristics of the Soshu tradition, one of the five traditions (Gokaden) of Japanese swordsmithing.