The commanding officer of the establishment or unit that owns the mess is permitted access to all his messes; thus a ship's captain has access to his vessel's chiefs' and petty officers' mess, the commanding officer of a regiment may enter any of his regimental messes, and the base commander of a Canadian Forces Base is welcome in any of his base's messes. In practice, commanding officers rarely enter anything other than the officers' mess unless invited, as a point of etiquette. In addition, duty personnel — such as a duty NCO or officer of the watch — or the military police have access to any and all messes for the purposes of maintaining good order and discipline. Chaplains are usually welcomed in all messes.