In the attached jpeg is a clip from my IDW showing part of a cross-section. The o-ring groove shown in the cross-section has an angled wall, and I'd like to dimension it just the way it is dimensioned in the handbook (the dimension circled in red in the jpeg).
What is the correct way to do this?
(I can put a center mark on the radiused bottom corner, use that as a reference, and then make the center mark invisible. But that offsets the vertical line from the wall, and makes the dimension less obvious to understand.)