It never occurred to me to mark it - but I tend to use whichever side when I cut.

I'm so glad this topic came up. I've been using two 5x24" rulers for yrs. & had never considered that happening. I had to check them & find they are still flat. No curve. I have sliced little knicks off the edges with rotary cutter but have affected their use.
Thanks for bringing this up. I will now ck. them once in awhile.

The new rulers are so much better now then the old ones with the raised black lines, yellow markings or printed measurements. Some things are better updated.

Very glad your cutting problem is resolved. However, I am confused by this sentence,

"When I finally set it on a straight surface - like my kitchen counter - I could see that my ruler was making a shallow arch".

I retired a craft table that was a great space saver because it had two roomy hinged leafs. After the pressure from countless cuts, the leaves curved downward from the center (where the support was) to the edge of the leaves. It took me a long time to figure out why my cuts all curved. The cutting mat was curved to the shape of the top of the leaves, too.

New ruler, new cutting mat and using the dining room table solved the problem. Thank God!

I check my 6x24" ruler on my granite counter top every few months too. I've had it since 2010 but I think I'm ready for a new one.

Starting the cut a few inches from the end and rolling backwards is especially important when you are cutting through eight layers of fabric at once, as you do when you make a Stack 'n' Whack. I always teach my students to do that.
If you push in from the edge, the pile of fabric is likely to wrinkle up from the pressure.

Thanks for mentioning this. I had no idea that that could happen. I'm going to check my older rulers.

I had to replace one of mine too for this reason. It was very hard to get rid of that old friend.

I think some of the plastic that they use in making rulers is softer than others. I have a favorite ruler that needs to be replaced as my new rotary cutter has shaved some filings off the side.

Marcia

When I first read this posting early this morning, I pooh-poohed the idea. I've been cutting and sewing all day. Just now, while waiting for my iron to heat up I decided to hold the edge of my ruler vertically against my dining room table. Well, no more pooh-poohing from me! The middle of my ruler swings easily back and forth while the ends stay flat. I would never have thought this could happen. Luckily I have a new 24" ruler that I bought when Hobby Lobby had a huge coupon. Thanks so much to the original poster!