>To do this one pair of sissors and one piece of paper are needed. By eye
>cut the paper to match the angle. Insert into angle. If to small start
>over. If too big cut down to fit. when it fits correctly touching each
>side use your protractor to measure angle. I use this also to measure
>width such as a tube diameter.
>Charles the architect Nighbor
>Walnut Creek, Ca
Before I got that angle protractor from my daughter's surgeon, I tried this method and didn't care for the amount of trial and error needed to get it right. I eventually settled on this method which seems to take less time: Take two strips of light card stock (index cards or shirt stiffener card) and tape one to the inside centerline of the tube (sort of like they do the numbers on race bikes. If you have three hands you can skip this step and go on to the next one...). Hold the second strip against the other tube so that it overlaps the first strip and and then staple or tape them where they overlap. If you cut a tiny notch to fit over the lug tangs you can get an extremely accurate measurement.
Bob Hovey
Columbus, GA