Abstract: At 10:10 a.m. on April 18, 1988, Employee #1 and a coworker were preparing to frame a shed on the roof of a six story building under renovation. A 4 ft by 15 ft piece of corrugated steel was lying on the roof in their way. Neither of the employees knew that the piece of steel covered a 3 ft by 3 ft opening in the roof. The employees picked up the piece of steel by the long end, and began to walk with it. Employee #1, who could not see the surface he was walking on because of the size of the steel, stepped through the roof opening and fell through a gutted stairwell shaft to the basement floor. He died of brain injuries 4 hours later at the hospital.