A wall is then built within the brackets. Then the finished treads are bolted set up. These treads can be of steel or Wooden or wood clad metal. Cantilever techniques have to be developed by a structural engineer, so that they remain horizontal and rigid with use after some time. https://staircaseinspirations.weebly.com/blog/the-rise-of-cantilever-staircases-in-contemporary-homes