shirasaya

A katana blade fitted with a plain wooden grip and sheath (saya) that, when fitted together, completely conceal the blade and resemble a bokken. This configuration was intended to be used for storage or transportation of blades, not combat, since in addition to the decorative furniture characteristic of katana, a blade in shirasaya also lacks a hand guard (tsuba), making it unsafe to wield. Despite this fact, it's not uncommon for shirasaya blades to be depicted as weapons in active use.

The signature sword carried by Zatoichi, the blind swordsman and eponymous protagonist of the Zatoichi films, resembles a shirasaya; however, the blade is straight and the purpose of the plain wooden furniture is not to protect it in storage, but rather to disguise it as a blind man's cane.