repair of the wooden components of the ship. He supervised the Caulker, the Carpenter's mate and the Master-at-arms. Cockpit mates Originally, a master's mate was an experienced petty officer, who assisted the master, but was not in line for promotion to lieutenant. By the mid-eighteenth century, he was far more likely to be a superior midshipman, still waiting to pass his examination for lieutenant or to receive his commission, but taking rather more responsibility aboard ship. Six master's mates were allowed on a first rate, three on a third rate, and two on most frigates. Senior petty officers A Midshipman was an apprentice officer who had previously served at least three years as a volunteer, officer's servant or able seaman, and was roughly equivalent to a present-day petty officer in rank and responsibilities. After serving at least three years as a midshipman or master's mate, he was eligible to take the examination for lieutenant. Promotion to lieutenant was not automatic, and many midshipmen took positions as master's mates for an increase in pay and responsibility aboard ship. The Clerk was a literate worker who did administrative work on the ship. The Armourer maintained and repaired the smaller weapons on the ship. The Caulker maintained and repaired the caulking of the ship's hull. The Ropemaker made, maintained and repaired ropes on board. The "Master-at-arms" was a naval rating, responsible for discipline aboard ship, assisted by Corporals. Petty officers The Yeoman of the Sheets was in charge of the rope store. Given that the ship was rarely dry inside and the ropes rotted when wet, preserving the rope was a major problem. See also Ship transport References External links United States Coast Guard Merchant Mariner Licensing and Documentation web site Nautical terminology Sailing