Abstract: Employee #1 and coworkers used two 15-ton Mack winch trucks to load a 97 ft, 45,000 lb derrick onto two lowboy trucks that were positioned back-to-back. After the derrick was crated, Employee #1 began to tie down the bottom end of the bolster on the lowboy. One of the rope slings used to lower the derrick was still attached to it, and a coworker attached the other end of the sling to the side of winch truck #323 by the hook. As the winch truck pulled away from the derrick to make room for Employee #1, the bottom of the derrick was pulled off the lowboy trailer. Employee #1 was struck by the derrick and pinned beneath it; he was killed. Coworkers had failed to remove the sling attached to the winch truck before it moved away from the derrick.