The swords of the samurai were highly prized and carefully maintained. They were kept in a sheath (saya) when not being used, and stored horizontally to prevent undue pressure on the blade edge or moisture buildup that can lead to rusting. Regular cleaning and maintenance is also important.
To make a katana, the swordsmith began by heating iron sand and charcoal in a clay furnace to generate crude steel known as tamahagane. Then the blacksmith hammered and folded the metal multiple times, to give it a layered impression. This process, called mukushiage, made the harder outer layer (kawagane) wrap around a softer iron core (shingane), creating a sword with the strength to resist breakage and the flexibility needed for cutting.
After the forging is complete, the smith plunged the blade into a trough of water for a rapid cooling process known as quenching. This causes the back edge and inner core to contract faster than the kawagane at the front of the blade, which naturally bends the sword to give it its distinctive curve.
Once the blade is cooled, the smith uses files and planes to refine its shape. The he then sharpens the blade to a razor sharp edge. The katana’s tip can be long (okissaki), short (chukissaki), or curved forwards like a spearhead (ikuri-okissaki). In addition, the blade may have decorative markings (horimono) engraved in Japanese characters or motifs such as dragons. Some of these markings are purely aesthetic, while others are intended to help the samurai distinguish his blade from those of his fellow warriors in a combat situation. The keywords I will use are