Answer:
Or, while Ninjas stealthily negotiate their way through dark places (such as an enemy’s residence at night), ninjas used the scabbard as a walking stick, feeling or probing their way around objects so as not to knock into anything and alert the enemy.
Perhaps the ninja’s most sinister use of the scabbard was to put a mixture of red pepper, dirt, and iron shavings at the top of the scabbard, so that when the ninja drew his sword, his opponent would be blinded.