Abstract: Employee #1 was part of a two-man crew that was erecting and assembling a derrick. At the time of the incident, the two employees were rigging up the work floor. Part of that job is to hook the floor chains connected to a cable coming from the top of the rig. The cable is connected to the floor chain which had a hook without a latch at the end of the chain. The crew was trying to install the elevators. They had brought the elevators over the handrails when somehow the one or both chain floor hooks came off. Employee #1 fell through an opening created by the separating of a floor grating when the oil derrick platform floor collapsed. Employee #1 fell approximately 8 ft to the ground and suffered a fracture of the L3 vertebrae. Employee #1 was hospitalized.