A procedure can look complete on paper and still fail the moment it meets heat, noise, time pressure, missing tools, changing weather, equipment wear, and competing production demands. That gap is the space between work-as-imagined and work-as-done. It is one of the most useful ideas in modern health, safety, and environment practice because it shifts attention from blame to learning. It asks a better question: What does the system ask people to do, and what does the real job