This chapter is the continued part of Chapter 4| Names of the Parts. Please read chapter 4| Names of the Parts before reading part 2.
Let’s discuss how to find the Koshi-zori or Chukani-zori. Chukan-zori is also called torii-zori or Kyo-zori. Chukan-zori means the highest curvature comes around the middle, and for Koshi-zori, the highest curvature comes lower than the middle. Any sword looks like a curvature comes around the middle area, especially the photo of a sword in a sword book. That is because a sword is placed to fit in a given available rectangle space.
The correct way to look for a curvature is to stand the nakago (茎) perpendicularly. That way you can see where the curvature comes more precisely. If the Nakago is not vertical, the curvature comes in the middle on any sword. When you look at a sword, the first thing to do is to hold a sword so that the nakako is perpendicular. When you look at a sword in a book, rotate (move or shift) a book slightly so that the Nakago is perpendicular. You can see the real curvature of the sword in this way.