Abstract: At approximately 2:50 p.m. on September 16, 2010, Employee #1 was working as a welder for a manufacturer of truck trailers. He had just finished welding an upper coupler assembly, and he was grinding down rough spots on the welds. An upper coupler assembly was a structural component that became part of semi-truck trailers. It weighed approximately 1,000 pounds. The upper coupler assembly was clamped to a shop-fabricated rollover fixture during the welding and subsequent grinding processes. This rollover fixture rotated the coupler assembly to various positions so that a welder could reach all areas needing to be welded. When the welder was finished, the rollover fixture rotated the coupler assembly upside down to be unloaded and carried away to the next manufacturing process. Three clamps were normally used to secure the coupler assembly onto the rollover fixture during the welding process. At the time of the incident, one of the clamps was not installed. Employee #1 activated the control to rotate the coupler upside down. He was walking past the coupler assembly as it rotated, when the coupler assembly fell out of the rollover fixture, landing on him. Interlocks on the welding clamps had been removed. These interlocks, if present, would have prevented the rollover fixture from moving when the clamps were not installed. Employee #1 sustained a fractured pelvis and internal injuries. He was hospitalized.