Hi Terry, if it's exactly straight in one direction like it looks (if it is a trimmed portion of a cylinder) then curve-to-curve flow I think would work between an arc and a line. If you can post the .3dm file of your shape I could test it.

If the ruling lines are not all in the same direction then there isn't any tool in MoI to flatten it but you could get it done using the UnrollSrf command in Rhino that can flatten developable surfaces.

- Michael