Bright Check is a Red work wire which is made of a triangular shaped coil of fine wire - there is a hole through the center.  The triangular shape acts like the facets on a gemstone to reflect light in different directions, making it sparkle.  The wire is slightly flattened to give a very shiny surface.  This thread is delicate until it is stitched down. Use Bright Check by stitching through the hollow center, like you would apply a bead.  Use doubled thread with a good coat of beeswax.