The kama is a traditional farming sickle, and considered one of the hardest to learn due to the inherent danger in practicing with such a weapon.
The point at which the blade and handle join in the "weapon" model normally has a nook with which a bo can be trapped, although this joint proved to be a weak point in the design.
The edge of a traditional rice sickle, such as one would purchase from a Japanese hardware store, continues to the handle without a notch, as this is not needed for its intended use.
I remember one time Kise Fusie remarked during a clinic I attended,
that on Okinawa, every household had kama, as it was the way they gardened their household.