The Collaborative International Dictionary of English v.0.48:

Fretwork \Fret"work\, n. [6th fret + work.]
   Work adorned with frets; ornamental openwork or work in
   relief, esp. when elaborate and minute in its parts. Hence,
   any minute play of light and shade, dark and light, or the
   like.
   [1913 Webster]

         Banqueting on the turf in the fretwork of shade and
         sunshine.                                --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fretwork
    n 1: framework consisting of an ornamental design made of strips
         of wood or metal [syn: lattice, latticework,
         fretwork]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "fretwork":
   arabesque, basketry, basketwork, cancellation, cross-hatching,
   crossing-out, filigree, fret, grate, grating, grid, gridiron,
   grille, grillwork, hachure, hatching, interlacement, intertexture,
   intertwinement, lace, lacery, lacework, lacing, lattice,
   latticework, mesh, meshes, meshwork, net, netting, network,
   plexure, plexus, raddle, reticle, reticulation, reticule,
   reticulum, riddle, screen, screening, sieve, texture, tissue,
   tracery, trellis, trelliswork, wattle, weave, weaving, web,
   webbing, webwork, weft, wicker, wickerwork