You learn something new every day

I don't have much use for hair grips, as I have very short hair, but I do use them to keep my fringe off my face when I'm running. At the weekend, I learned that apparently you're supposed to use them with the wavy side down. That's a new one on me, but I tried it whilst running today, and for the first time only needed to use one, rather than 2. So it must be true!