I show you how to create a system which determines that you are cooking with exactly one sapling or stick in a furnace. The idea of using saplings as keys I credit to cubehamster. I don't know who invented the glowstone BUD here, but you can look at cubehamster's Sharing is Caring 1 video (http://www.youtube.com/watch?v=G3nnjv...) for that. I believe this particular combination of designs is original, though. Enjoy!