Abstract: At approximately 1:30 p.m. on August 3, 1997, Employee #1, of Robinson Pipe & Mechanical, Inc., moved a 4 by 8 ft sheet of 3/4 plywood that covered a 30 in. wide by 33 in. long opening in the second floor. At the time he did not realize the plywood was covering a hole and he wanted to move it from the center of the floor so he could roll a steam header on a steel cart from the north wall to near the west wall for installation. As Employee #1 lifted the plywood, he accidentally stepped through the opening and fell approximately 22 ft to the first floor. He was killed. The plywood covering the opening was not marked "hole" or "cover" as required by the 29 CFR 1926.502(i)(4). Also, it was not secured to the floor, as required by 29 CFR 1926.502(i)(3). The JSC Construction Company had placed plywood over the three holes after completion of the slip forming of the floor to guard the openings according to the 29 CFR 1926.502 standards. JSC employees spray-painted "no step" on the plywood, but they failed to secure it against movement due to wind or accidental displacement by equipment or by employees. The plywood that was originally placed by JSC had been used by other subcontractors for other construction operations, and the holes were re-covered by unmarked plywood, which hid the openings but did not alert other workers of the fall hazard that existed underneath. The prime contractor on the construction project was aware of the openings in the second-level floor but did not properly monitor this existing hazard. The company was not aware of the full regulation that required the marking and securing of the covers; this was an indirect cause of the accident.