ube quilting mentioned on this thread
http://www.quiltingboard.com/main-f1...e-t288400.html
about her ruler getting worn down and then her strips had a curve in them.
I have had this happen with my rulers, too.
It took me a while to figure out why - when I moved my ruler - and had not moved the fabric - why the edge of the fabric was not "straight" on the measuring line.
Turns out that i had worn a curve into the edge of the ruler. When I finally set it on a straight surface - like my kitchen counter - I could see that my ruler was making a shallow arch.
Of course it caused me pain to discard the ruler - but it caused me more pain to have wonky strips.