Jack is the name of several guards belonging to the Sheriff's Men.
Another Jack is a guard of Nottingham Castle's Castle Dungeons. He escorts a disguised Robin into the castle to 'shrive' the captured Hob, Hal, and Dicken. Roger and Giles try to get a loan from Jack. But Giles owed Jack money and knew that wouldn't work. When Robin tries to escape from the celler in the Trip to Jerusalem Pub, Jack steps behind him, and blocks his way back into the celler. Later Jack shows up at the tournament, as one of the guards asking for the entree fee.