An employee was moving a steel ventilation louver with a chain fall attached to a crane hook. The louver was then transferred to a chain fall attached to the ship. The louver was then lowered into position. The lover was sitting on the lip of the foundation and held back with another chain fall attached to the ship to prevent crushing the ship's signal box. The louver was disconnected from the crane hook to move into position. While the employee was repositioning the louver to a second chain fall, it slipped off the foundation and fell on the employee's right foot. The employee's toe was amputated while in the hospital.