Abstract: On October 14, 2009, an employee and a coworker, painters, were assigned to dismantle a van trailer, as a fill-in project. Previous work stripped the trailer to the floor, the front and rear cross rails and side rails. Flooring between the cross brace was removed in the front section of the trailer. This created a ladder configuration in the front section. Aluminum rivets securing the side rails were removed for the last twenty-five feet of the trailer on each side and the floor was cut transversely in between the last and second to last cross brace. The two rivets retaining the rear cross rail were left in place. As reported this was an attempt to allow the floor to drop out of the perimeter frame consisting of the front/rear cross rails and the side rails. A forklift raised the rear of the trailer 3 to 5 feet, while the employee struck the floor with a hammer while standing on the ground. At this time the bottom rail violently separated from the floor striking the employee in the forehead. The resulting trauma fractured the employee's skull, which required major surgery and extensive therapy. The employee was hospitalized. The employee claimed to have twenty-one years of work experience as a heavy duty truck and trailer mechanic, although did not exhibit competency for dismantling operations. Inspection of the trailer showed the inboard sealing lip of the bottom rail interlocks with the flooring that would prohibited the floor from "dropping out". A major factor contributing the structural failure was torsional loading on the side rails and subsequent release of energy created by lifting the trailer.