Abstract: Employee #1 was setting up a work platform so his crew could install insulation in a wall backstage of a high school auditorium. He was using a 26 ft aluminum extension ladder on a metal catwalk to reach a landing 9 ft above the walkway. The ladder slipped and Employee #1 fell approximately 9 ft, severely injuring his right knee. The ladder's foot pads had been removed, which increased the probability of it slipping on the metal catwalk floor. Employee #1 did not inspect the ladder for defects, nor did he tie, block, or secure the ladder. The ladder slipped and Employee #1 fell from about the 9 ft level. His right knee was severely injured.