Simple, cute--and it works! This was a Christmas gift from my friend D. I've used it every day since Christmas morning. It keeps my yarn clean and flowing smoothly. It stops the ball of yarn taking unplanned journeys across the room. And I'm anticipating the extra bonus of keeping my knitting out of the jaws of my yarn-eating cleaning robot.
I'm also hoping to use it to help wind off my smaller cones of yarn when making a warp, or skeins for dyeing. The larger cones are nice and stable, but the smaller ones have a bad habit of falling down unexpectedly. All in all a very clever little gadget!