Sentence:  And that's how it came to pass that on the second-to-last day of the job, the convict crew that tarred the plate factory roof in the spring of forty-nine wound up sitting in a row at ten o'clock in the morning drinking icy cold, Bohemia-style beer, courtesy of the hardest <WSD>screw</WSD> that ever walked a turn at Shawshank State Prison. 
Meaning of the word marked with <WSD> tags:  A prison guard.