hi there, Those are placed under the spool, so between the base of the machine and the spool of thread. They help reduce spool spin back lash. So it helps keep the spool from continuing to spin after you’ve stopped sewing. I’m not positive but I think you only need to use it if you’re on a vertical pin. A lot of the new machines have a vertical and a horizontal pin option. This depends on the type of thread you’re using. You’ll notice that on the more expensive thread like Gutermann, the thread on the spool is wound on a criss cross design, while thread like Dual Duty Coats and Clark are wound just around the spool, one line right after the other. Those that are like Gutermann should be placed on the horizontal pin and those that are like Coats should be on the vertical. Because of the way Gutermann is threaded, on a horizontal pin, it shouldn’t spin as much. The older machines only have the vertical pin so if that’s what you have, I wouldn’t worry about it and just use your felt. Hope this helps.
the_professors_assistant.
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