Abstract: At the time of the accident, Employee #1 was cleaning up an area of a flat roof when he lost his footing and fell through a sky light opening measured 47-in. by 46.5-in. landing on the second floor deck. The fall distance was measured to be approximately 12 ft from the roof top to the second floor. The sky light openings were guarded with multiple 2-in. by 4-in. boards and plywood secured to the roof top the night before the incident and had remained guarded in the morning when Employee #1 began his work. Someone from the other trade or Employee #1 himself had removed the cover to facilitate the transport of materials prior to Employee #1's fall. Employee #1 could not remember how he fell or the detail of this incident. Employee #1 was only able to confirm the opening he fell through was not guarded at the time. Employee #1 suffered a puncture injury and was hospitalized.