Hitomezashi is a variation of the Japanese technique Sashiko. You can decorate, reinforce, or repair with the technique. Hitomezashi means "one-stitch sashiko" because the pattern you create is built up stitch by stitch, while other sashiko patterns are built up with entire rows of stitches where each stitch is not critical to the pattern.
In this set, you get instructions, a leather palm thimble, sashiko needles, and 20m of white thread, in addition to 2 A6 sheets with a grid printed on Solufix.
Solufix dissolves in water. Use them by sticking them to the fabric where you want to sew, use the grid as a template for the pattern you want to sew, and then rinse it away so that only the stitches remain.