Bo-Hi (Blood Groove) Styles on Samurai Katana Swords

In addition to the standard full length groove that terminates either just before or actually under the habaki, blade collar, there are several less common variants.

One such variant is the double bo-hi, which has two - shallower - fullers instead of one. However, from a practical viewpoint, the effect on handling is the same as a single, deeper fuller - the only difference is, it is perhaps more visually interesting.