It's Knot Shellac

All the benefits of Shellac but it's "knot". It's "Knot" Shellac minimizes grain raise, blocks tannins, and provides an overall even, non-blotchy coverage for stain as a pre-stain conditioner. It penetrates & seals wood grain fibers, creating a waterproof barrier that can be used on bare wood as well as under paints and top coats.