Abstract: Employee #1 was operating a Disco Side-O-Matic hydraulic unloader that was mounted on a flat bed truck. He was unloading cubes of concrete blocks from the truck. He had unloaded seven cubes and was raising the forks to unload the eighth cube. Employee #1 raised the forks, which were attached to a block and hook on a wire rope. He raised the block to the trolley of the boom. The block was pulled tight into the trolley. The block turned sideways, allowing the forks to slide out of the hook and fall on Employee #1. Employee #1 sustained severe head lacerations, a fractured wrist, and injured his back.