The sageo is the cord threaded through the kurigata — the small knob on the saya — and historically it was used to tie the scabbard securely to the wearer's obi, or sash. Beyond that practical function, it also served as a quick-release binding for the saya during formal situations, and skilled practitioners developed specific sageo techniques as part of traditional iai and kenjutsu systems. On a collectible katana today, the sageo retains all of its visual and cultural significance: its color, braid style, and material directly influence the sword's overall aesthetic composition. A blue sageo, with its cool tonal quality, creates strong visual contrast against black lacquer saya while complementing gold or copper tsuba metalwork — making it one of the most popular accent choices among collectors seeking a cohesive display piece.