The selected feature could not be converted to a circular line or arc
CF Image, I got this error message when I wanted to dimension between my beam and my sheath (red and blue line)... I don't understand why it refuses to rate that... Yet my beam is rectangular, like my sheath...
Otherwise you have to select the 1 of the two strokes, click on another line that is perpendicular to this 1st stroke, click on sketch point to get the intersection point, then do the same thing for the second stroke.
If I followed the thread of your questions correctly, your beam must be an imported body (or even a surface). If I followed correctly too, you had big problems importing your building. So I think that the beam you are trying to dimension (or at least hang a dimension) is not a straight line but a spline!!
SW refuses doc to hang a rib on it!
If that's right, the way out is to place a point (or other remarkable entity like a line) on your view and attach the desired dimension to it (I'll prefer a point, with a line, you risk having an angle and not a straight one). You will also certainly end up with a value with tenths in decimals.
So, I tested several things, the intersection point but given my context, the less I do, the better because if for each side I create an intersection point or another sketch, it makes me waste too much time given the loading of my pc... If I start doing this, either I quit or I smash the window with my tower...
Then, dimensioning with another piece could have been not bad but as it's to help the fitters, if I put a reference point 8 meters from where they have to put the duct, it's my forehead that will break the window;D
For flat surfaces, it doesn't do it all the time, like for the edge that bugs, some work, others don't...
Finally, I managed to solve my problem by activating the filters, so I only select the edges and it works:p
Oh yes, and I'm going to put Benoit in the best answer for two reasons, first of all, I don't care about the points, I'll never have a grail:( And then, since he has a very good memory, that he perfectly relocated my situation and that it made me happy that he remembered all my problems, I think he deserves the best answer;)