Rabbi Eliezer says that one may take a chip of wood from the house and use it as a toothpick and he may gather wood from the courtyard for firewood because everything in the courtyard is considered prepared for use. The Sages say that one may only use wood in the house as fuel (but not wood from the courtyard, nor for other purposes).
One may not light a fire on yom tov, such as by rubbing sticks together, nor may one heat tiles to cook on them (because doing so tempers the tiles). Rabbi Eliezer said that one may stand in the storage shed before Shabbos in a Sabbatical year and say, “I will eat from this produce tomorrow” and that is adequate preparation. The Sages say that one must mark and specify exactly which produce he will eat.