箱乱刃 (Hako Midareba)
What is Hako Midareba in Japanese Katana terminology?
Hako Midareba is a type of blade pattern (Hamon) in Japanese swords. It is a kind of ""乱刃"" (Midareba: irregular pattern). This blade pattern (Hamon) is characterized by its very narrow and wide tempering widths repeating alternately, and its angular appearance reminiscent of a box, hence the name ""箱乱刃"" (Hako Midareba).
In the shallow tempered part of the Hako Midareba, the blade pattern (Hamon) may disappear as a result of repeated polishing. This phenomenon is referred to as ""刃が駆け出す"" (the blade running out). This is one of the characteristics that can be seen in the process of using and maintaining a Japanese sword.