Hard light, also spelled hard-light, is the Forerunner technology that allows light to be transformed into a solid state to bear weight and perform a variety of tasks. The technology is used in energy bridges as well as to lock Forerunner doors.[1]
Background
Hard light was commonly used in the construction and composition of Forerunner structures, and as a covering for mechanical and technological mechanisms, such as on the arms of a war sphinx.[2]
Many Forerunner ships use hard light technology to form its internal divisions and compartments. This allows a Forerunner ship to easily reconfigure its layout, furnishings or decoration at will.
Most Forerunner structures project a hard light decorative shell over the structural support elements of the building. Almost all Forerunner buildings seen thus far lack this covering, suggesting that they may be in a "deactivated" state. It is also possible the Forerunners didn't install hard-light generators on Halo's structures, as they were meant to be purely functional.