Phillips, Flat, Plastite-Alternatives. Thread Rolling Plastite 48-2 screws are used in thermoplastics, engineering resins and certain thermosets. The 48° thread profile increases holding strength while reducing material displacement. Flat head screws are used when protrusion of the fastener above the mating surface is unacceptable. Typically 100 degree flat or for fastening softer materials, 82 degrees flat.