gratings
ˈɡreɪtɪŋ
noun
a framework of parallel or crossed bars, typically preventing access through an opening while permitting communication or ventilation.
framework,grid,grate,network,grille,grillwork,lattice,trellis,criss-cross,matrix,mesh,gauze,netting,net,web,webbing,tracery,interlacing,reticulation,reticulum,plexus,graticule,decussation