Nice system. I think I'd cut out a bit of adhesive whiteboard material and draw dots on that, but that has its own downsides.

Little systems like this are so useful. For example, I have a similar system for clothes hanging in my closet. Shirts hang on the left side of the bar, trousers on the right. Empty hangers go into the middle. Clean clothes are always placed into the middle on the appropriate side. Whenever I pull something out to wear, I choose from the ends, not the middle.

This does two things: First, I'm cycling my clothes a little more fairly instead of wearing the same stuff over and over (the DS&A nerds among you would call this an LRU cache, I guess). Second, clothes that I don't like so much or just don't use, for whatever reason, get pushed to the ends, and every year I pull out the stuff that's been stuck at the ends for a while and donate it to charity, without a moment's thought.