Abstract: Employees were in the process of covering up three openings on the second floor of a building under construction. They were spacing 4 in. by 6 in. timbers of 12 ft and 16 ft lengths over the openings, planning to nail plywood on top of these. Steel post guards with cable top and midrails were in place surrounding the openings, which were for two elevators and an air shaft. The foreman had told his men not to go under the cable guard railings while they were placing the stringers. The foreman and another carpenter had gone to the basement to look for materials when another worker came by and offered to help. He was told not to go under the railings, but he did not listen. He sat on a foot-wide separator between two openings and began pulling and spacing the stringer beams. As he pulled on one beam, the other end fell through the elevator opening. His end flew upward, knocking him off the ledge. He fell about 46 ft to the elevator pit below. He was hospitalized.