Black belts are commonly worn for all dan ranks in several martial arts. In others, different colors are utilized, with the highest grade (10th dan) wearing a crimson belt in certain systems. 6th to 8th dan in Judo may wear a red and white-patterned belt, whereas 9th to 10th dan may wear a full red belt. In Karate, black belts are awarded at 1st dan and above; below this level a student wears a brown belt. Only black belts are allowed to teach classes, so this symbolizes their status as the most advanced students in their schools. However other grades may be involved in assisting with teaching activities such as testing or grading papers. The term "black belt" comes from kenjutsu, the Japanese art of sword fighting. In this system, black means expert and belt number indicates rank. So a black belt is someone who has reached the highest rank possible in aikido.