An accident investigation was conducted in a commercial high-rise office building. The investigator started with where did the accident happen. It occurred on the fourth floor. The next question was, "When did it happen?" The answer: it happened at 11:15 AM. This was followed by, "What happened?" A worker fell off a step ladder while installing ductwork. Then: How did the fall occur? The worker was working on the top step of the ladder when he lost his balance and fell.  || Martin Lloyd Sanders ||