Tachi
The tachi that can be seen in museums have one or more chips along the back of the sword, while the cutting edge looks almost untouched and mirror polished. The experts explain that Samurai made the smallest possible moves with their tachi to kill the enemy. Thus when both swords were about to collide, the samurai both turned their swords and let only the blunt back (mune) of the blades hit one another. The cutting edge was used for finish touches, namely for cutting the human body.