The seppa is a small metal spacer used on both sides of the tsuba (handguard) of a katana. It serves as a buffer between the tsuba and the habaki (blade collar) to prevent wear and damage to the sword during use.
The seppa is usually made of brass or copper, and its shape and size can vary depending on the design of the sword and the preferences of the craftsman. Some seppa are circular, while others have a more oval shape or a more complex design.
When assembling a katana, the seppa is placed on either side of the tsuba, followed by the habaki, which is slid over the blade. The tsuba is then placed on top of the habaki, and the seppa serves as a space between the tsuba and the habaki.
In addition to its practical role of protecting the sword, the seppa can also be decorative. Some sword makers engrave patterns or characters on the seppa, which adds to the beauty and artistry of the katana.
Overall, although the seppa may seem like a small and insignificant part of the katana, it plays an important role in protecting the sword and is an important part of its design and aesthetics.