On Nihonto (Japanese swords), the tsuba (hand guard) is not meant to
prevent the opponents swords from striking the hand, but rather to
prevent the users hands from slipping onto the blade. Hence many are
small and somewhat "delicate" sukashi (cut out) styles. It is rare to find
a tsuba with a sword cut on it.
Rich S
The Japanese Sword Index
http://www.geocities.com/alchemyst/nihonto.htm