In the early 20th century, nothing quite fit — fire hoses couldn’t connect to one another, football teams played with different balls, traffic lights meant different things in different states. Then World War II exposed the deadly cost of incompatibility, and the US quietly imposed a single solution on production lines across the world: the 60-degree screw. Roman Mars and historian Daniel Immerwahr tell the story of a hidden industrial empire, built one standard at a time.