What is Hi-kaki in Japanese Katana terminology?

"Hi-kaki" (樋かき) refers to the process of carving a groove, known as "Hi" (樋), into the blade of a sword. This groove is not only decorative but also functional. It lightens the blade, improves its balance, and allows for a smoother withdrawal of the sword from its scabbard. The presence of a Hi can also affect the sound the sword makes when swung. The process of Hi-kaki is a delicate one, requiring a high level of skill and precision from the swordsmith.