I never thought of that, but it should work.

I'd guess you turn it sideways, hold it level, point the line on the outer ring at the sun, count the number of degrees from O the line points to, and that's the angle of the sun.

I think The Old Farmer's Almanac has those numbers for sale for your location. They have an online app that will make them and send them to you for the entire year (for one location). It's handy for designing buildings to take advantage of solar gain.

I never thought of the sundial trick either, thanks for those cool tips!!