Timber Framers Guild Forums Training Asian Timberframing and Joinery methods of setting-out, from Asian

Center lines are used in French Scribe methods. On the end make two lines corner to corner. Plumb through the intersection and level through the intersection, then chalk the four lines. Make sure your stick is level first (with level mark).

Some of us also use centerlines during hip roof framing (especially when two different pitches intersect). All jacks and purlins are given centerlines on their top faces (the faces in the roof surface). From there all lengths are measured from where these centerlines meet the offset line of your hip. Then through different scaled drawings and a calculator measurements can be found regarding jack and purlin lengths.