The Bow, a sign of respect for the Dojo (training hall), instructor and for students and of course dicipline. We bow on entering the Dojo,its the first thing we do, and before we start a kata etc, but it is so much more than just a bow as i always tell my students everything you do in karate is self-defence. The bow is an really good and vital self-defence technique, it can be used as a brutal headbutt while ones hands may be in their pockets as someone is giveing a lot of verbal abuse,as there may be no means of escape and have no choice but to attack first in order to stun the assailant and create a gap for a follow up technique or to simply stun and run. Secondly you may be grabbed from behind (bear hug) trapping your arms,again hands may be in pockets if cold wheather, thrusting the buttocks backwards,loosening the assailants grip etc,or from the same attack could even be a throw if the assailant is caught of guard. It can also be used in grappling wheather stand up or on the floor but it is just then a headbutt but i refer back to the bow.
Really hope this is of some interest.