On a drawing, I have put a section view through the centre of a hole. The hole has a 2mm x 20° chamfer/lead-in.

I now need to dimension the hole using the 'chamfer dimesion' option.

I cannot select the correct edge for the detailing. I've tried adding a constrained sketch, still cannot create.

Is there a special way to annotate chamfers that on a section view, or to select the correct edge in a fancy way?