Alright, so I am creating parts and drawings from exisiting drawings that came from AutoCAD, so the customer can see the parts in 3D. However, I am having a little trouble with the way they dimensioned some of the parts. The parts are mostly rings or cylinders, and the drawings all have section views to show the cross-section of the rings. I want to dimension the diameter of the rings to the line in the section view (see attached image), but I can't figure it out. I have tried making the dimension in the front view, and then holding shift and dragging it over, but all I get is a red circle with a cross through it. Are there any tricks to get this to work? Any help is appreciated... Thanks.