The bokken or wooden sword
The effectiveness of the wooden sword or bokken is demonstrated by Musashi’s famous fight against his father's murderer Sasaki. Musashi knew that Sasaki used a very long straight sword, so he cut himelf a wooden sword from a pole, slightly longer than Sasaki’s.
During the fight, as Musashi had predicted Sasaki’s sword reached as far as Musashi’s forehead but only enough to cut through the cotton band protecting his head. His bokken on the other hand reached as far as Sasaki’s head, killing him.
Since the Ashikaga era, the bokken has increasingly taken the swords place in competitions, thus reducing the number of injuries and deaths. It is actually modelled on a real sword (whilst the bo and jo are rounded staves) Nowadays, it has beome a training aid in many budo disciplines, including karate and aikido.