Screw and washer assemblies are commonly called "SEMS™" when they are preassembled. The innovative SEMS™ products are another major fastening invention by ITW Shakeproof that changed the industry. Tooth lock, helical spring lock, dished type and conical washers, to name a few, can be preassembled to machine screws, as well as, thread forming, thread cutting and self-drilling screws. These combinations offer unique capabilities that would otherwise be unavailable for easy and efficient assembly operations.