Although it is not a myth that these holes were created to hurl items into the spaces below them, including projectiles, large stones and caustic lime, their uses were even more complicated. They could act as safe observation points from which the wall footings or a passageway could be seen. If fires were started, either accidentally or deliberately during a siege, the slots could be used to douse the flames with water.
For the most part, castles were rarely besieged, and murder holes were mostly left untested. In fact, many of them were intended to be nothing more than symbols of architectural prestige.