A line on the forward side of the compass bowl representing the bow of the ship and used to steer a course
A mark on the bowl of a marine compass or diving compass which indicates the boat or divers heading.
A mark or permanent line on a compass indicating the direction forward parallel to the keel when properly installed.
A lubber line is a fixed-line displayed on a compass binnacle or radar plan position indicator display pointing towards the front of the ship or aircraft and corresponding to the craft's centreline.