Go to a local machinist and get some scrap carbon steel, say a strip of 1/16 and drill a hole in it. Or ask them if they could help you out but drilling steel that thin will be easy and you could do it with a hand drill on your own if you have to. If the steel is already heat treated you will now have a striker that will throw much better sparks and will do so longer than your hacksaw blade.

No using a knife as a striker is never recommended, a knife is quite possibly your most valueable survival tool in the wild so it is best not to abuse it. If you have no other choice use the very back of the blade (the section of the cutting edge closest to your hand) this area is used least frequently and will not be as missed as the middle of the blade or the tip. A better idea is to use the spine of the blade as you will not damage your cutting edge at all. Still, having some sort of striker is always best, in my experience having the right kind of striker makes a world of diference in using flint or magnesium and flint together. For more check out my thread on flint, steel and firestarting. Hope this helps

-Olaf