In Attack on Titan, the blades used with the 3D Manuever Gear have notches in them similar to those found on craft knives:
Certain knives like the one above come with snap-off points so that when the blade dulls, it can be removed and replaced by a fresh and sharp piece. However, a utility like this seems redundant on the 3DMG blades as a shortened blade would be extremely ineffective at removing a Titan's neck, not to mention that the blades seem to be used and discarded as a whole piece.
Additionally, The wiki page on the blades themselves gives no mention of the notches.
So is there any reason for the notches to exist aside from looking cool?