What is Koshibi in Japanese Katana terminology?

The term "Koshibi" (腰樋, こしび) refers to a specific type of groove (Hi) carved into a Japanese sword. This groove is typically located in the lower third of the blade, near the "waist" (Koshi) of the sword. The Koshibi is a type of "Bohi" (棒樋), which is a straight, long groove running the length of the blade. A typical example of a sword with a Koshibi is the "Naginata" (薙刀), a type of traditional Japanese pole weapon. The presence of a Koshibi can affect both the weight distribution and the aesthetic appeal of the sword.