Whenever I need to use my ruler to make strips or to make pattern adjustments, I would use a piece of masking tape at the line I was measuring to - this is how it is done in design rooms when I worked in the garment industry. It's very practical so you don't have to keep looking for whatever number your working with.
Rare "Light bulb moment" ...
I made an "ruler marker" by sewing a piece of elastic together (tight fit) and sliding it onto many of my rulers. I keep a few without it because it can get in the way of certain uses (rotary blading).
It's one of those little things that makes pattern altering run just a bit smoother.