Their specialty was re-rolling worn out railroad rails .
During the American Civil War specialty also rolled out cannon , iron rail , and 2 - inch - thick ( 51 mm ) sheets of iron to clad the CSS Virginia for the Confederate navy .
Their specialty was re-rolling worn out railroad rails but during the American Civil War it also rolled out cannon , iron rail , and 2 - inch - thick ( 51 mm ) sheets of iron to clad the CSS Virginia for the Confederate navy .