More to explore:
Another version and 'how to' for constructing a toothbrush rug.
Crochet Rug - with instructions
Toothbrush Rug 2
Toothbrush rug by Secretsugar, via Flickr
Toothbrush Rug Instructions | eHow
How to make a toothbrush rug.
How to Make Crocheted Rag Rugs | eHow These are definitely the most specific I've seen for instructions, they read like a pattern for folks who know how to crochet already.
toothbrush rug tutorial
Detailed rag rug instructions using an old toothbrush whittled into a needle for braiding/weaving
How to Make a Toothbrush or Naalbinding Rag Rug