I wanted to have an anchor for some soft nylon cord, http://www.nylonnet.com/merchandise/?item_id=1573&cat=473 #84 White braided mending twine, that would allow me to pull the corners of a sheet taut. This is the best of a series of experiments I tried, varying tooth shape and angle. The design is driven by Inventor's parameters, so can be adjusted to suit other cords.I used the academic version of Autodesk Inventor Pro (free to retired folk) under Parallels 10 beta on a MacBook Pro to design this. On my second try, with a clean start, I got it parametrically defined so it was easy to vary dimensions to try different sizes until it fit my cord well.