Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Great for backup or using as a main way to light fires.

I've been using my Magnesium/Flint bar for about 15 yrs. You do not need a sharp knife or even a knife at all. You just need something with a good solid hard edge. I always use mine by using the back of my knife to scrape the magnesium into a pile for semi-damp tinder. I use the back of my knife as well to spark the flint onto the tinder. I highly suggest getting one of these, and I also like my "Swedish Firesteel" as well for lighting camp fires.