Does your ruler still have a perfectly straight edge?
I just verified that one of my favorite rulers has a curve on both edges from being worn down by use.
I can slide a folded index card under the centers when I stand the ruler on edge.
Is it significant? It's enough so that when I move the ruler, the cut edge does not follow a straight line on the ruler.
So - now to replace that ruler - it's a 3 x 18 ominigrid with the 1/8 inch markings. It is/was one of my favorite rulers - which is probably why it is worn down.
Doesn't it seem odd/irritating/frustrating that the used items wear out sooner than the unused ones?