What is Hiraji in Japanese Katana terminology?

The term "Hiraji" (平地, ひらじ) refers to the area of a Japanese sword that extends from the Shinogi-ji (鎬地, the ridge area) to the cutting edge. When appreciating a Japanese sword, this area is primarily the focus. The Hiraji is the flat surface of the blade and it is where the beauty of the steel and the skill of the swordsmith can be most appreciated. It is here that one can observe the Jigane (地鉄, the steel's grain pattern) and the Hada (肌, the pattern of the steel folding). This terminology is used to describe the specific characteristics of the sword's structure, contributing to its overall aesthetic and functional design.