One of the things I make is flint & steel firekits. Whole kit is a steel striker, a good flake of flint, some charcloth to catch the spark and a tin to keep it in. No problem to make except for the flint. Which you don't make, you find. And you need good enough quality flint that it'll strike a spark from the steel without breaking.
Lots of places to find flint(depending on where you are), and you can order the stuff. Dixie Gun Works carries both a bag of good flakes and flint nodules so you can try your hand at knapping. But I'd always wanted to go out and find some nodules and knock off my own flakes. No luck so far.
Then at Medieval Fair a gentleman came by to get a couple of strikers; said he'd lost the ones he got last year. Talked for a bit and found that he's an archeologist(retired) who knaps flint as a hobby and as a teacher for students at OU. When I mentioned I was about out of flint he said he had some pieces I could have.
So the other day finally got time to go by his place and get some. And he threw in a short lesson on flint knapping, and a short lecture on where in the state I could find some if I had a chance to go looking for it.
I'd bought a nodule from Dixie once before and tried knocking off flakes with, let us say, not the best of results. With a good hammerstone and his demonstration, earlier today I took one of the chunks and knocked off a number of good, usable flakes(as opposed to my earlier success in turning a flint nodule into sharp-edged gravel).
I get time I want to mess with this some more; try making some knives and arrowheads. Good flint or obsidian is brittle, but a flake can be unbelievably sharp. We're talking 'feel a tug and notice blood' sharp. Matter of fact, I've read that eye surgeons are using scalpel blades cut and polished from obsidian; the edge is smoother and sharper than steel, it can actually cut cells without tearing the edge is so fine.
He bet me a striker that within three months I'd want more flint to work on, said it's addictive. I need to make him a couple.