Oh wow, I felt this one in my bones. My husband and I have been trying to keep track of his blood pressure pills for years and we have tried everything. A little chart on the fridge, a phone alarm, even one of those fancy caps that light up when you open it. You know what actually works? Flipping the bottle over, just like you said. It takes zero effort and my brain can see it from across the room. The fancy stuff always ends up in a drawer somewhere, but turning a bottle upside down is something I can actually keep up with.

Did you ever try weighting the middle of the string or using a line level to check for sag? I used to swear by string lines for everything, thought a laser was just a fancy toy guys used to show off. But after hearing about your corners getting pulled out of whack in the heat, it makes me rethink that. A laser stays put no matter how hot it gets, and a story pole does not stretch or dip in the sun either. Maybe the old school way is not always the best way once you get past a certain span.