The purpose of a makiwara, as said above, is to FORCE you to strike correctly. The heavy bag is for general traning and while not more important will be used a great deal more. Most people just can't spend 20-30 minutes hitting a makiwara. If your doing it right it hurts without causing damage. If your not doing it wrong it hurts and causes damage. Definalty have somebody show you exactly how your suppose to use one. Also, always start makiwara training slow each time. Nothing worse than thinking your good to go and hitting hard with an bad fist angle.