True, but I can't bet on finding 3 rocks of equal height at any moment. Most abundant natural stuff around me is sand. Lots and lots of sand.
I can bet more on "human-made junk" that is scattered these days in the remotest of areas. Three semi-crushed Pepsi cans maybe.

Something like that
Because there are black ones and grey ones.

Agree with you and have been thinking to buy the IKEA thing to make a stove but have been delaying it

Yesterday I got 3 cans of baby formula which are almost same size of the IKEA strainer. While I was thinking over which was better, a related question popped in my head.

When it comes to solid metal cans, I use something like this to make triangular holes.



One row near the bottom and one row near the top

Rest of the can remains solid
And if you see the IKEA video, you notice some of the flame escaping out of the stove.
While in solid cans, air comes in, smoke comes out, but fire remains mostly IN.

Question is : how much of ventilation holes are enough ??

It doesn't take a lot

ican youcan
tincanium /
Micro Gasification 2.0 Cooking with gas from dry biomass.pdf

I have made the later one. Works perfectly well when you finally ignite the top (tricky part).

OK

Another question about making fire

I have seen a you tube about single flints like these



These are replacements in single flint strikers , and they are a micro copy of a ferro rod.

It is too hard to hold a ingle one by fingers but the good thing is that they have a threaded head which a genious guy in you tube attached to an eye screw



and .. you can attach it to a keychain or whatever and should actually be able to hold it and use it.

I couldn't find the right size screw to attach to but in any case use it while attached to a modified striker just to see what kind of material it would produce sparks. Is it "strike anywhere" as long as it is iron or what ??

Sadly it did not strike

I used a file , knife, hacksaw .. and many other items that did in fact produce sparks with a ferro rod, but not with this baby ferro.

So, what are your thoughts ???

How fast were you striking?
How much force did you put into it?
How sharp/pointy is the file/hacksaw/knife?
Try rubbing the flint/ferrocerium on the file instead of rubbing the file on the flint

Maybe you can mount a butane/lighter wheel and use that to throw sparks

fold a piece of tin/metal around the baby ferro
punch two holes with a nail and secure the wheel in holes
then fold tin around bottom of baby ferro,
where you punch holes so screw can pass through ....

probably easier to cut down a bic/butane lighter

If you strike a butane lighter/bic, when you're its when the wheel gets up to speed that sparks

To me it looks like somebody is trying to sell tons of his broken rods to inventive preppers The spark wheel idea is good, but the mount should not be permanent, as the rod will be shaved unevenly that way and will stop working after a while. I'd try running it over a file fast, like a match on a striker. But it may start chipping.