Gauge: a metal thickness measurement.
Glass felt: glass fibers bonded into a sheet with resin and suitable for impregnation with asphalt in the manufacture or bituminous waterproofing, roofing membranes and shingles.
Glass mat: a thin mat of glass fibers with or without a binder.
Glaze coat: (1) the top layer of asphalt on a smooth-surfaced built-up roof membrane; (2) a thin protective coating of bitumen applied to the lower plies or top ply of a built-up roof membrane when application of additional felts or the flood coat and aggregate surfacing are delayed. See Flood coat.
Granule (also referred to as mineral or ceramic granule): opaque, natural or synthetically colored aggregate commonly used to surface cap sheets, shingles, and other granule-surfaced roof coverings.
Gravel: course granular aggregate resulting from the natural erosion of rock.
Gravel stop: a flanged device, frequently metallic, designed to prevent loose aggregate from washing off the roof and to provide a continuous finished edge for the roofing.