Thanks Box: I Can't tell you how many different angles I had tried without success, but got this to work as you suggest. I was trying to get the dimension to show in the same plane as the stand face, which I still can't do without going to the work around that Dave R provided. I see in the reference below how inferences can be tricky, with Google suggesting zooming as the only solution to overcome it. Doesn't seem to help in this case, however, but I'm not very good at Zooming/Panning with the mouse when I am dimensioning so maybe that is my problem.

http://productforums.google.com/forum/#!topic/sketchup/5j-vQ4HfLpw

I have a Logitech LX5 Cordless Laser Mouse that wouldn't orbit using the scroll wheel. I have just discovered the solution from a Logitech forum, to re-assign the scroll wheel to "middle button". Works great now

http://forums.logitech.com/t5/Mice-Software/LX5-can-t-orbit-or-pan-in-3DS-Max-or-SketchUp/td-p/198517

Thanks for the quick response Dave R. This looks like a good work around. I guess the trick is to know what SketchUp can't do! I spent a lot of time trying to find a way to make it work but I have found that the more the pain, the greater the lesson, so hopefully I will remember this.

I have designed a simple music stand which is now ready to dimension. Since many of the components are set at an angle, I can't get the dimension tool to work. For example the distance between points A and B on the attached drawing. Any help would be appreciated

Music Stand.skp