Abstract: Employee #1 and a coworker were installing aluminum window frames on the fourteenth floor. Because the frames had high headers, they were welding from a 5 ft manually propelled mobile scaffold. They were having trouble installing a header and used a 2 by 4 to spread the vertical molds so that the horizontal header would slide into place. Employee #1 was hitting the 2 by 4 with a hammer when the board popped out. The momentum of his swing carried Employee #1 forward, causing him to fall 14 stories. He was killed. The employees were not tied off nor had they locked the scaffold wheels prior to starting work.