In Japanese culture the Hachimaki has long been a valued symbol of ones dedication to a certain task. In the formal Taijutsu classes students wear it as part of their uniform (Gi).
It represents the student's seriousness toward training, as well as it's practical use to absorb sweat during intense training.
The two Kanji characters on the hachimaki say Konki, which means "Strong Mind/Spirit".
This reminds the student of the need for
perseverance, persistence and endurance.
As the student progresses through the various levels different colour hachimaki are worn. Interestingly the colours roughly are opposite to the belts, starting at black and ending in white. The White Hachimaki is a symbol of the student coming full circle, having finally achieved Muga Mushin - No Self No Mind.