1) Center line 2) Line 3) Two-lane road feature 
The center of the boat: from the stern to the bow.
[n] - a line that bisects a plane figure
A linear line running through the center of the bow’s handle and extending through the middle of the limbs to the limbs’ tips.
center line noun a line that bisects a plane figure
any line that bisects a plane figure: the centerline of a building plan. · a line along the center of a road or highway dividing it into separate sections for traffic moving in opposite directions. · the perpendicular bisector of the line connecting two radio transmitters.