Question: Does the Mishnah support R. Chanina (Rov takes precedence over Karov)?

Answer (Abaye): There is no proof for R. Chanina, because the case in the Mishnah is where there is a platform in front of the nest.

Answer (Rava): There is no proof for R. Chanina, because the case in the Mishnah is where there are two nests, one on top of the other.

Obviously, if he prepared the birds in the lower one but not the birds in the upper one, and then on Yom Tov he found birds in the lower one and the upper one was empty, that the birds are prohibited, (we assume that the birds he prepared flew away and the ones that he found hopped down from the upper nest).

But even if he prepared the birds in the upper one but not the birds in the lower one, and then on Yom Tov he found birds in the upper one and the lower one was empty, those birds are also prohibited, (we assume that the birds he prepared flew away and the ones that he found climbed up from the lower nest to the upper one).

Question: What is the scenario where this is permitted?

Answer: In a case where the birds are able to fly.

Question: Then perhaps the birds he prepared flew away and the birds he finds are other birds!

Answer: Rather, it must be referring to birds that cannot yet fly, but can only hop.

Question: If there is another nest within 50 Amos (the range of hopping birds, as taught by Mar Ukva), then perhaps the birds he prepared hopped away and the birds he finds are birds that hopped to here from the other nest (and if there is no other nest within 50 Amos, then it goes without saying that these birds are permitted)!?

Answer: There is another nest within 50 Amos of this nest, but it is around a corner.

We might have thought that the birds will hop to that nest, since it is within their hopping range (and the birds one finds in the nest are not the birds that he prepared and they are prohibited).

The Mishnah teaches that the birds that he finds in his nest are permitted, because a bird that hops will only hop as long as it can see its own nest.

(Beis Shamai): A crushing board may not be moved in order to cut meat.

(Beis Hillel): It is permitted.

(Beis Shamai): A hide may not be laid down before those who will trample on it, nor may it be picked up unless it has at least a k'Zayis of meat on it.

(Beis Hillel): It is permitted.

(Tosefta)\: Beis Shamai and Beis Hillel agree that if one already cut meat on the crushing board, it may not be moved.

(Abaye): This applies only to a wheat-crushing board, but everyone agrees that a bone-crushing board is permitted to be moved.

Question: That is obvious, for the Mishnah mentions only a wheat-crushing board (Ali)!

Answer: You might have thought that a bone-crushing board is also prohibited.

the reason the Mishnah mentions only a crushing board is to teach the extent of Beis Hillel's leniency, that even a Davar sh'Melachto l'Isur is also permitted to be moved.

Therefore Abaye tells us that everyone agrees that a bone-crushing board is permitted.

Alternate answer (Abaye): My statement is only necessary to teach about a brand new bone-crushing board.

You might have thought that even a new bone-crushing board is subject to the argument between Beis Shamai and Beis Hillel, Beis Shamai prohibiting it because one might change his mind after moving it and decide not to use it.

Therefore Abaye tells us that everyone agrees that a new bone-crushing board is permitted (and Beis Shamai is not concerned that one will change his mind).

Question: But we learned that Beis Shamai is concerned that one will change his mind?

(Beis Shamai): It is prohibited to bring a slaughterer and knife to the animal on Yom Tov, and to bring the animal to the slaughterer and knife (because the owner might change his mind).

(Beis Hillel): It is permitted.

(Beis Shamai): It is prohibited to bring the spices and crusher to the pestle, and to bring the pestle to the spices and crusher (because the owner might change his mind).

(Beis Hillel): It is permitted.

Answer: The cases of an animal and spices are different, because one is likely to change his mind if he finds a fatter animal, or if he decides to bring a cooked dish that does not need spices (whereas here, he will not change his mind, since he already slaughtered the animal, he surely will use the bone-crushing board to chop the meat).

(Tosefta): Beis Shamai and Beis Hillel agree that one may salt meat, which will be roasted, atop the hide.

(Abaye): This applies only to salting meat for roasting, but it is prohibited to salt meat for cooking on top of a hide.

Question: That is obvious, for the Mishnah mentions only roasting!

Answer: Abaye is teaching that not all meat to be roasted may be salted (it is prohibited to salt meat to be roasted in the manner of salting meat for cooking).

(Tana Kama of the Beraisa): It is prohibited to salt fats and to turn them over (so that they not rot).

(R. Yehoshua): They may be spread out in the wind on posts.

(R. Masneh, first version): The Halachah is like R. Yehoshua.

(R. Masneh, second version): The Halachah is not like R. Yehoshua.

Question: While in the first version, R. Masneh is teaching a needed Halachah (we might have thought that the Halachah follows the majority), but according to the second version, what Chidush is R. Masneh teaching?

Answer: The Chidush is not to follow R. Yehoshua (whose reasoning seems logical (if we do not permit it, one will refrain from slaughtering an animal on Yom Tov and thus refrain from Simchas Yom Tov).

Question: (According to second version of R. Masneh) Why does that case differ from the case of laying down a hide, which Beis Hillel permits (so that one will not refrain from Simchas Yom Tov)?

Answer: In the case of the hide, it is not obvious that it is being laid down for processing, because it is also fit to recline upon, but in the case of the fats, it is obvious that they are being spread out in order to preserve them, and thus one might think that it is also permitted to salt them.

(R. Yehudah citing Shmuel): One may salt many pieces of meat in one salting, even though he does not need all of them.

R. Ada b. Ahavah acted cunningly, and salted one piece of meat (in order to eat it) and then another.

(Beis Shamai): It is not permitted to remove a shutter

(Beis Hillel): It is even permitted to restore it.

Question: What type of shutters are Beis Hillel permitting (even to restore)?

Answer (Ula): Those of a merchant case.

(Ula): There are three listed actions which Chazal permitted in order to promote other causes.

Spreading the hide lest the person otherwise not slaughter meat for Yom Tov.

Restoring the shutters of the merchants, lest people otherwise not be supplied with the spices for Yom Tov.

Restoring a bandage on Yom Tov (in the Mikdash) lest one otherwise avoid doing the Avodah.

(Rachba citing R. Yehudah): Another instance is permitting (according to R. Yehudah) the goods which may have been touched by an Am ha'Aretz, even after the Regel has passed, lest storekeepers otherwise would not open their stores to the public on the Regel.

Question: Spreading the hides is a Mishnah (wherein Beis Hillel permits this)!?

Answer: We might have understood Beis Hillel as permitting because of other Yom Tov uses, and thus permitted even a hide from an animal slaughtered before Yom Tov (and not restricted to those slaughtered on Yom Tov it owing to Ula's explanation).

Question: Restoring the shutters is also a Mishnah!?

Answer: We might have understood Beis Hillel as permitting it based on Ein Binyan b'Kelim.

Question: Restoring a bandage is also a Mishnah!?

Answer: We might have understood the Heter as due to Ein Shvus b'Mikdash (and even a non-serving Kohen could take advantage of the Heter).

Question: Opening the Chavis (and deeming it Tahor) is also a Mishnah!?

Answer: We might have understood that Chazal saw Tumas Am ha'Aretz as Tahor on the Regel (and thus permitted even that which was not begun to be sold).

Question: Why didn't Ula mention Rachba's case?

Answer: He was only teaching undisputed cases.

Question: But the other cases are all subject to Machlokes Beis Hillel and Beis Shamai!?

Answer: We don't regard Beis Shamai as a contest to Beis Hillel.

Our Mishnah (which teaches that Beis Shamai and Beis Hillel argue over the removal of the shutter) is not like the Beraisa in which Beis Shamai is presented as arguing only over restoring the shutter.

According to that Beraisa, Beis Shamai is only arguing over restoring shutters on hinges (since that is considered Binyan).

Without a hinge, all agree it is permitted.

Question: But another Beraisa teaches that they argue only when there is no hinge, while all agree that with a hinge it is Asur!?

Answer (Abaye): A side hinge is universally Asur while a top hinge is Mutar; the argument is only over a hinge in the middle of the shutter (which is not absolutely like Binyan and may [Beis Shamai] or may not [Beis Hillel] be subject to a Gezeirah of Binyan).