Domestics Stop Motion Screw is a mechanism used while winding the Bobbin with the Bobbin Winder so that stitching is temporarily stopped. As the title implies adjusting screws, also known as back-up screws, stop screws and preset screws, are not just a simple set screw. They are a screw with a purpose--three actually. The first is to provide a fixed stop for a cutting tool to rest against during tool changes.