An employee was walking on stilts (raised up about 3 feet), installing batt insulation in the ceiling (about 8-feet high) with a manual staple hammer. The stilts caught a piece of plastic insulation bundle wrapping, causing the employee to lose his balance on the stilts. He tipped forward on the stilts, striking the floor with his knees. His coworkers offered to help him back up, but they couldn't move him. He was hospitalized with a fractured spine.