: I thought I said that.

: The thread doesn't solve the problem of putting the centerlines in pencil.
: Which, although not required, is nice to have for reference.

Snapping a chalkline is not a precise method. Depending on how you grab and release the line your mark may be off.

However, if the line is stretched taut, you can go over it with a MIST of paint from a can of spray paint, held 2 to 3 feet above the work. Spray the air above the line and let the paint mist fall by gravity onto the work. The very light mist dries almost immediately. When you remove the line you'll be able to see the shadow the line leaves. Sharp, thin, and precise. It is more permanent than chalk, but so thin that it sands off easily.

I use this method for establishing a centerline on my strongback.

PGJ