The Collaborative International Dictionary of English v.0.48:

Sley \Sley\, n. [AS. sl?, fr. sle['a]n to strike. See Slay, v.
   t.]
   1. A weaver's reed. [Spelt also slaie.]
      [1913 Webster]

   2. A guideway in a knitting machine. --Knight.
      [1913 Webster]

   3. (Weaving) The number of ends per inch in the cloth,
      provided each dent in the reed in which it was made
      contained an equal number of ends. --E. Whitworth.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Sley \Sley\, v. t.
   To separate or part the threads of, and arrange them in a
   reed; -- a term used by weavers. See Sleave, and Sleid.
   [1913 Webster]