And for sparking on the magnesium block's ferrocerium, the back of a saw blade, be it the woodsaw in a multitool (Leatherman is very good, Gerber is good, can't saw first hand or observation for SOGs or Vics) or a SAK (the Vics are good, Wengers are OK), is better than trying a knife blade. All you are doing is beating on the edge while getting a minimum number of sparks.

Best bet, in my experince, is a bit of hacksaw blade. Snap a piece off, add a hole if needed so you can't loose it. And practice. People try to wittle on the mag block, and that isn't what you want to do. You want to scrape, like it was a hide or an arrow shaft- no sharp edges or points needed or wanted. Just a nice, crisp edge. I recommend getting a second one to practice with. And don't get a cheap one, buy the Doans ones, they are the best.

I case you couldn't tell, I like my magnesium blocks, but I was given my first one when I was 9. I've been playing with them for a while. :P But given my druthers, I'd rather use a sparklite, they are faster.