Abstract: Employee #1 and four coworkers were on the penthouse floor of an elevator construction project. Unknown to them, the concrete floor contained two floor openings, each 36 in. square and covered by an unsecured 1/2 in. plywood piece measuring 48 in. square. In preparation for the repositioning of the elevator control box, the employees were removing all scraps of wood from the east side of the floor. Employee #1, who was facing south, picked up the plywood covering the east side floor opening, took a step forward as he raised it, and fell approximately 25 ft through the opening to the concrete floor. He struck a metal trash chute which was suspended below the penthouse floor and landed in a sitting position. Employee #1 sustained a broken hip, fractured vertebrae, a lacerated tongue, and a bruised shoulder. Causal factors include lack of training, 1926.21(b)(2), and improper installation of floor opening covers, 1926.500(f)(5)(ii).