I'm new to Tormek but a collector of fine knives. I've seen in some tutorials that there is a black protective covering between the jig and the knife blade, which seems safe and reasonable, especially if the knife is worth more than a T-8. Looks like it's a thin black rubber square, but I have not seen it offered anywhere. Does anyone know what it is and how to get or make one? I sure don't want to scratch a good blade, and I don't want to loosen the jig's hold on the knife.