The shinogi-zukuri (pronounced "shin-o-gee zoo-koo-ree") is the most common katana and tachi style. Throughout the history of Japan, shinogi-zukuri styled katanas had subtle differences. Some were wider and thinner. Some were narrower but thicker and slightly more diamond shaped in terms of cross-section (this allowed for a sword to be less prone to bending - a trait especially helpful in harsh battlefield applications). The shinogi is the ridge of the sword. Some had grooves or hi in the flat of the blade above the ridge line.

Note that the tip is not a crude triangle nor is it a "reinforced armor-piercing chisel point" as often mispresented in knife industry marketing, but the ridge line of the tip and the edge of the tip both follow the arc of larger concentric circles.

ILLUSTRATION BY ADRIAN KO