Katana sheaths, known as "saya" in Japanese, are traditionally made from wood and are carefully crafted to fit the specific sword they are designed for. The process of making a katana sheath involves several steps:

1. Wood selection: A suitable piece of wood is chosen for the saya construction. Traditional choices include Japanese hardwoods like magnolia (ho wood), known for its lightweight and moisture-resistant properties. Other woods, such as rosewood or even bamboo, can also be used depending on the desired aesthetic and functional requirements.
2. Rough shaping: The selected wood is cut and shaped into a rough form that matches the contours of the katana blade. This is typically done using woodworking tools like saws, chisels, and rasps.
3. Hollowing: The interior of the saya is hollowed out to create a snug fit for the blade. This process involves carefully removing excess wood from the core while ensuring that the blade will slide in and out smoothly. Specialized tools like gouges and files are used for this step.
4. Final shaping and sanding: The rough-shaped saya is refined through further shaping and sanding to achieve a smooth and contoured surface. This includes refining the curves, beveling the edges, and ensuring a comfortable grip.
5. Lacquering: The saya is coated with multiple layers of lacquer, typically urushi, a natural lacquer derived from the sap of the urushi tree. Each layer is applied, allowed to dry, and polished before the next layer is added. This process provides protection and durability to the saya while giving it an attractive finish.
6. Fittings and finishing touches: Once the lacquer has fully cured, the saya is fitted with the necessary metal or horn components, such as the kurikata (cord knob) and koiguchi (mouth of the sheath). These fittings are typically secured with small bamboo pegs or glue. The saya may also be adorned with decorative elements like inlays, carvings, or paintwork, depending on the desired style.

It's important to note that the process may vary slightly depending on the specific style and region, as well as the skills and preferences of the craftsman creating the saya. Traditional Japanese swordsmithing and saya-making are intricate crafts that require experience, precision, and attention to detail.