or cen·ter line
Examples from the Web for centerline
The check valves are placed slightly below the centerline of the boiler (fig. 18).
The check valves are placed slightly below the centerline of the boiler (fig. 18).The 'Pioneer': Light Passenger Locomotive of 1851|John H. White
A single leeboard was fitted and secured to the hull with a short piece of line made fast to the centerline of the boat.The Migrations of an American Boat Type|Howard I. Chapelle
The opposing surface is not flat, but slopes away from the centerline like a boat's bow.Following the Equator, Complete|Mark Twain (Samuel Clemens)
Daoud climbed a ladder, raised the heavy door, and found himself on a walkway built over the centerline of a roof.The Saracen: Land of the Infidel|Robert Shea