Hard light was used extensively by the Forerunners for a variety of purposes. The control panels and interfaces found in many Forerunner installations are composed entirely of hard light, and can react to the touch of a Forerunner or Human despite their utter lack of mechanical components. Hard light was also commonly used in the composition of Forerunner structures and ships, either for aesthetic purposes or as a covering for mechanical and technological mechanisms, such as on the arms of a War Sphinx. Hard light is also used in the locking mechanisms of Forerunner doors. Light bridges made of hard light are common throughout Forerunner installations; these bridges are strong enough to bear the load of heavy objects such as a M808B Main Battle Tank, yet can be switched on or off as easily