Distinction: However, a Stam Marzev is of wood. People do not make it of stone.

Question: We should distinguish regarding a Mazchilah itself, between one of stone and one of wood!

Answer: The Tana prefers to teach in our Mishnah that there is a Chazakah for the place of a Marzev.

Implied question: There were many [Chachamim] whose fathers and grandfathers were Chachamim, and we do not say about them ha'Chut ha'Meshulash..., only here!

Answer: This is because all three of them saw each other.

Implied question: Why does it mention R. Oshaya before his father R. Chama in their argument?

Answer: It is because he was much greater than him, like it says in Eruvin (53a) "the heart of latter Chachamim is like the opening of the Heichal. This refers to R. Oshaya";

Also, it says that R. Oshaya in his generation was like R. Meir in his generation. His colleagues could not understand his true intent.

Explanation: R. Tam explains that we discuss a Mitzri window, but a Tzuri window, or one made for light, which is a fixed matter, even above four Amos it has a Chazakah.

Proof: A Beraisa above (22b) [taught regarding the Mishnah (22a)] that windows, both above and below, the Shi'ur is four Amos...

Regarding this, the Beraisa teaches below (one who comes to build a wall opposite his neighbor's window, if it will be lower, must make it at least four Amos lower), lest he stand and see.

Inference: Even above four Amos, it has a Chazakah, since it is a fixed matter.

Rebuttal #1 (Rashba): This is no proof. Even though it is above four Amos for one who stands outside, [perhaps] for one who stands inside it is not above four Amos, e.g. the windows are in an upper story.

Rebuttal: #2: Perhaps the case is, he has witnesses or a document [that he has a Chazakah for the window, but Stam, no window above four Amos has a Chazakah].

Explanation: Even the owner of the roof can protest against the owner of the Chatzer.

Suggestion: Perhaps only the owner of the Chatzer can protest against the owner of the roof, but the owner of the roof cannot protest against the owner of the Chatzer!

Rejection: The Seifa teaches that less than a Tefach, he cannot protest. Rav Huna explains that the owner of the roof cannot protest against the owner of the Chatzer, but the owner of the Chatzer can protest against the owner of the roof!

Inference: You are forced to say that when it is a Tefach, even the owner of the roof can protest against the owner of the Chatzer.

Explanation: This is because on a Tefach, one can put big things that are heavy on the wall, or if he puts a Kli full of water and it spills, it ruins the wall.

The owner of the Chatzer can protest [against the owner of the roof] due to Hezek Re'iyah.

Implied question: The Gemara thought that Rav Yehudah is not concerned for Hezek Re'iyah. (If so, why can he protest?)

Answer: In any case, when he puts a Kli full of water, sometimes it falls, and the entire Chatzer is sullied. Sometimes it falls on the head of the owner of the Chatzer.

Explanation #1: We discuss within three [years]. After he made a Chazakah, the owner of the Chatzer cannot protest against the owner of the roof.

Explanation #2: We discuss only after three [years]. The owner of the roof can protest against the owner of the Chatzer;

This is not due to the reason I gave. Rather, because the owner of the roof has rights to use the ledge, he wants to use it at all times, and not let the owner of the Chatzer use it;

However, within three, when he did not yet make a Chazakah, he cannot protest against the owner of the Chatzer. However, the owner of the Chatzer can protest against the owner of the roof, just like according to Rav Huna, when it is less than a Tefach.

Implied question: Why does he distinguish between a Tefach and less [than a Tefach]?

Answer: It depends on this. If it is a Tefach, Chazakah helps for it, so he can protest against the owner of the Chatzer;

If it is less than a Tefach, there is no Chazakah, so he cannot protest.

Implied question: Regarding a ledge in front of a window that goes out to Reshus ha'Rabim, in Eruvin (98b) we permit to leave on it only Kelim that will break (if they fall), for we are concerned lest they fall, and he will come to bring them (from Reshus ha'Rabim to his house)!

Answer #1: Here we are not concerned lest it fall on the head of the owner of the Chatzer, for he does not stand there constantly under the ledge.

Answer #2: There we forbid only to put things on [the ledge]. Here we discuss hanging from it. Regarding something that hangs, we are not concerned lest it fall.

Question: How can the owner of the roof use the ledge? There is a wall [around his roof]!

We said above (2b) that if a roof is adjacent to another's Chatzer, he makes a wall four Amos tall!

Answer: The ledge is in a corner, at the end of the wall.

Explanation #1 (Rashbam): We ask why we taught specifically a joint Chatzer, for now he damages [at least] two.

Inference: He (the one who wants to open a window) is not a partner in the Chatzer.

Objection (Ri): We conclude afterwards [that the Mishnah forbids] even to a joint Chatzer, in which he can say "in any case, you needed to conceal yourself from me." This implies that he is a partner in it!

Explanation #2 (Ri): We ask why we taught specifically a joint Chatzer, in which he will damage him from two places (the Chatzer, and the window). Even to his friend's Chatzer, in which he will damage him only from here (the window, it should be forbidden)!

Question (Rashba): If so, why does it say "until now, you needed [to conceal yourself...]"? It should have said, the Chidush is that he says [back] to him "in two places, I cannot conceal myself from you!"

Explanation #3: Initially, when we asked, we did not think that he was a partner in the Chatzer.

Explanation #1: [Until now, I did not need to conceal myself] when you were in the house.

Explanation #2 (Rashbam): [Until now, I did not need to conceal myself] when I was in the house.

Rebuttal (Rashba): Also now, he need not conceal himself regarding using the house, for this window he opened is not opposite the door [of his neighbor's house], and not opposite a window!

A Mishnah below teaches that one may not open a window opposite a window. (The Tosefta forbids also a window opposite a door, or vice-versa.)