I used this when I made cheongpomuk muchim, but it can be used for a lot of things, usually fruits and vegetables to give them a fun zigzag edge.
My cookbooks
Which to get? my first book has all the recipes for all the essential Korean pastes and sauces, but my second book Maangchi's Big Book of Korean Cooking has more recipes. Both are best sellers and either one is a good choice if you want to learn Korean home cooking.