Cleat for soft nylon cord

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.