Short answers, pulled from the story.
The first practical application emerged in 1590 when slitting mills arrived from Belgium to England. These early machines passed flat bars between rolls to create iron plates before using grooved rolls called slitters to produce rods.
Three-high mills were introduced in 1853 to enable the rolling of heavy sections that earlier configurations could not handle. This system uses three rotating rolls where metal passes through two pairs sequentially without requiring reversal needs.
Hot rolling occurs when metal exceeds its recrystallization temperature, allowing grains to deform and then recrystallize without work hardening. Cold rolling happens below the recrystallization temperature, often at room temperature, which increases strength through strain hardening by up to twenty percent while improving surface finish.
Full-hard rolling reduces thickness by fifty percent, while half-hard and quarter-hard involve less reduction. Cold rolling cannot reduce thickness as much as hot rolling in a single pass but improves surface finish significantly.
John Wilkinson changed the industry landscape at his Bradley Works in 1786 by coupling a Boulton and Watt steam engine directly to a slitting and rolling mill. This innovation significantly enhanced production capabilities until electric motors displaced steam engines after 1900.