On many human worlds near Aslan space , resident Aslan accept some daggers of human make in duels, but not necessarily all . To identify suitable weapons, tassels, bound at the head by the sewa knot, are attached to the pommel. The use of sewa tassels is popular even on worlds that see few Aslan. Systems of coloring and tassel variations differ from world to world. Almost universally, however, black symbolizes either a high degree of skill or a large number of victories, while gray is generic, indicating no particular degree.