Abstract: Employees were installing a standing-seam roof. Employee #1 was operating a roof seamer and starting platform. He had been instructed in this operation and had performed this work 2 weeks earlier. After sealing approximately 190 degrees of the roof, he set the equipment in place. Before the operation started, the platform had to be clamped in place. However, an electric cord became tangled in the seamer, and Employee #1 had to pick up seamer to remove the cord and set the seamer in place again. After moving the unit, the employee either did not install clamp or installed the clamp improperly. The clamp failed, and the weight of seamer caused the rear of the starting platform to rise into the air. The platform struck the employee, knocking him several feet and causing him to fall 24 feet to ground level. He was hospitalized for injuries sustained in the fall.