I made one of these at the weekend...
I took two coffee cans, a small awl and my Leatherman SuperTool.
I used the awl to punch a lot of small holes and also a blade to cut out two larger holes in the bottom of one can, then used a can opener on the SuperTool to take out what is a perforated disc.
On the other can, I used the awl again to punch a lot of holes, over a height of about 2" from the bottom.
Then, in three places around the can, I cut out a V shape, and folded this inwards. These serve as brackets to hold up the grate, which will be around 3" above the base of the can, and also allow in more air, and allow me to light the fuel resting on the grate from below (one of the larger holes in the grate lines up with a hole in the side).
I had to crease the grate slightly to fit it into the can, but with the brackets sticking about 1/2" inside, there's no way it can fall right to the bottom. OK, so if I tried, I suppose I could have done that. But even I'm not that clumsy at four in the afternoon. Not usually.
So now that the stove was finished, I threw some paper and tinder in the bottom, then kindling, then slightly thicker stuff (nothing revolutionary there, then).
A match poked in under the grate made the paper catch, then the rest, and in a short while there were nice yellow and blue flames coming out of the top.
But as for cooking on it, no chance!
I was looking forward to making some proper coffee, but my coffee pot must have been trapping too much smoke inside. I just got a tar-like deposit on the bottom of the pot, tepid water inside it, and some charcoal...
OK, so the optimist in me says I have got myself a charcoal kiln. Or maybe even a producer-gas generator, if I tweak it... But really what I want is a hobo stove.
Back to the drawing board, I suppose.
Keith.