<fc #ff0000>Warning: Unmarked spoilers ahead.</fc>
Banners (Naya: ktemigsil) are a way for Nayabaru to ceremonially honour their allegiances and virtues.
Nayabaru usually do not wear clothes, unless the weather is too cold for comfort, but most Nayabaru tend to have banners for special occasions. Greeting visitors you knew would come may be such an occasion, or a special conference.
Since they can also convey allegiance, they provide good backup symbolism where tattoos cannot be applied. As of The Sky's Umbilical Cord, for example, Valcen often wears the banner of the Karesejat, a purple band.
The most common way Nayabaru wear banners is to place their centre against the back of their neck, then let the ends fall over their shoulders, then loop them around their upper arms once from there. Usually this leads to the ends falling from the inside of their elbows. If they are feeling especially ceremonial, they may scoop up the very ends with their hands, so the end segments of the banner hang down between elbow and hand.