I thought I'd share the method I just stumbled upon, and that seems to be working well for me so far.
These are called Bulb Pins, and are just a kind of little safety pin with a thin round loop and then a clasp. I've been putting them in a specific intervals when I need to measure a section that's longer that my weaving space. (Needing a 9" section, I put one in at exactly 3" and 6", you get the idea, I'm sure)
Found them at WalMart - Simple, precise, cheap and reuseable!