Abstract: Employee #1 and a coworker were assigned to install four skylights on a flat built-up roof. Another contractor had removed the existing built-up roofing material and all that remained was the existing metal deck at the four proposed skylight openings. Employees #1 and #2 installed wood curbing at the first proposed skylight opening. The coworker then began cutting the metal deck for the first skylight opening with a Sawsall saw. He cut one side, then asked Employee #1 to check the Sawsall case about 4 ft away for new blades. The coworker then started cutting another side of the proposed skylight opening. Employee #1 came over next to him and fell through the partially cut opening approximately 20 ft 6 in. to the floor. Employee #1 was killed.