Beitzah, Chapter 4, Mishnah 3. The Mishnah continues its discussion of preparing wood for kindling on Yom Tov, and adds a ruling concerning a house full of produce whose access has been blocked.
Splitting wood from beams:
We do not split wood from beams that were designated for building purposes. Such beams are muktzeh, since they are intended for building - a labor that may not be performed on Yom Tov - and therefore they may not be used for kindling on Yom Tov.
Even from a beam that broke on Yom Tov one may not split wood. At first glance, once it has broken it is no longer fit for building and stands ready to be burned; however, since at the onset of Yom Tov it was designated for building, the status of muktzeh took hold of it as the festival began, and it remains muktzeh.
The implements with which splitting is permitted:
When splitting is permitted, it may be done only with a shinui - in a manner different from the usual one, and not with the implements used for this during the week:
"Garzen" (axe) - forbidden.
"Masor" (saw) - forbidden.
"Magal" (sickle) - forbidden, even though it is not normally used for cutting wood but for harvesting.
"Kofitz" (cleaver) - permitted, since it is meant for cutting meat, so that using it constitutes a departure from the weekday manner - the departure required in order to split wood on Yom Tov.
A house full of produce that was breached:
A house full of produce that is ready to be eaten, whose entrance is sealed - with bricks or with stones that were not joined with mortar but merely placed one upon another - so that there is no way to reach the produce. If on Yom Tov the sealing came apart on its own and the entrance was breached, one may take produce from the breach that has opened up.
The reason: the produce itself was prepared, and only access to it was prevented. The prohibition against removing the sealing is only rabbinic, and in this case it even came apart on its own and not through human action. Therefore the lack of access is not enough to render the produce forbidden, and once it has become accessible it is permitted.
The view of Rabbi Meir:
Rabbi Meir says that one may even make the breach at the outset: to remove the stones and the bricks from their place, as long as no mortar joins them to one another, in order to reach the produce.
In summary: In this Mishnah we learned that one may not split wood from beams designated for building, nor from a beam that broke on Yom Tov, since the status of muktzeh took hold of it at the onset of the festival; that permitted splitting is done with a shinui - not with an axe, not with a saw and not even with a sickle, but only with a cleaver; and that in a house full of produce whose entrance was sealed and then breached on Yom Tov, one may take produce from the breach, and according to Rabbi Meir one may even make the breach at the outset, provided that no mortar joins the stones together.