The Collaborative International Dictionary of English v.0.48:

Nettles \Net"tles\, n. pl. [See Knittle.] (Naut.)
   (a) The halves of yarns in the unlaid end of a rope twisted
       for pointing or grafting.
   (b) Small lines used to sling hammocks under the deck beams.
   (c) Reef points.
       [1913 Webster]