The Gemara answers: With what are we dealing here in this baraita? It is a case where the wall has not been fully breached, but rather remnants of the wall remain on each side (Rabbeinu Ḥananel; Rif).

Rav Yehuda said: If several courtyards open onto a common alleyway, the residents of the houses in the courtyards are prohibited to carry in the alleyway, unless the alleyway is rendered fit for one to carry within it by placing a side post or a cross beam at its entrance, and by the inhabitants of each courtyard placing food in a common area for the duration of Shabbat, symbolically converting the entire alleyway into a single household. It is prohibited to carry in an alleyway that the residents did not merge. Nevertheless, if the alleyway was rendered fit by means of a side post placed at its entrance, one who throws an object into it from the public domain is liable; the side post functions as a partition, and the alleyway is deemed a full-fledged private domain. If, however, the alleyway was rendered fit by means of a cross beam, one who throws an object into it from the public domain is exempt; the cross beam functions only as a conspicuous marker. It is not considered a partition that renders the alleyway a private domain.

Rav Sheshet strongly objects to this due to the following: The reason that one is exempt in the latter case is due to the fact the residents of the alleyway did not merge. By inference, if they did in fact merge, one would be liable even if the alleyway was rendered fit by way of a cross beam. This, however, is difficult. One can ask: Does this loaf, through which the residents joined together to form a single household, render the alleyway a private domain or a public domain?

But wasn’t it taught in a baraita: Courtyards shared by many and alleyways that are not open on two opposite sides, whether the residents established an eiruv or did not establish an eiruv, one who throws an object into them from the public domain is liable. This seems to contrary to Rav Yehuda’s statement.

Rather, if it was stated, it was stated as follows. Rav Yehuda said: In the case of an alleyway that is not fit for merging, i.e., an alleyway that is open on two opposite sides, if the alleyway was rendered fit for one to carry within it by means of a side post, one who throws an object into it from the public domain is liable. In that case, the side post is considered a third partition, and since the alleyway is closed on three sides it is deemed a private domain. If, however, the alleyway was rendered fit for one to carry within in by means of a cross beam, one who throws an object into it is exempt.

Apparently, Rav Yehuda holds that a side post functions as a partition, whereas a cross beam functions as a conspicuous marker but is not considered a partition. And, so too, Rabba said: A side post functions as a partition, whereas a cross beam functions as a conspicuous marker. But Rava said: Both this, the side post, and that, the cross beam, function as a conspicuous marker.

Rabbi Ya’akov bar Abba raised an objection to Rava from the following baraita: One who throws an object from the public domain into an alleyway, if the alleyway has a side post, he is liable; if it does not have a side post he is exempt. This shows that a side post is considered a proper partition.

Rava replied: This is what the baraita is saying: If the alleyway is closed on one side such that it requires only a side post in order to permit carrying within in, one who throws an object into it from the public domain is liable because the alleyway already has three partitions and is therefore a proper private domain according to Torah law. However, if the alleyway requires a side post and something else in order to permit carrying within it, one who throws an object into it from the public domain is exempt because the alleyway has only two partitions and is therefore not considered a private domain.

He raised an additional objection to Rava from the following baraita. Furthermore, Rabbi Yehuda said: The halakha is as follows with regard to one who has two houses opposite each other on two sides of the public domain, if he chooses, he may create a private domain for himself in the area of the public domain. He may place a ten-handbreadth high side post from here, perpendicular to the public domain. This creates a symbolic wall which, in the halakhot of alleyways, has the legal status of a wall. And, he may place an additional post from here, on the other side, and that has the same legal status as if he closed the public domain on all of its sides. Or, he can implement a different solution appropriate for alleyways by placing a beam extending from here, from one end of one house, to the end of the house opposite it. This creates a symbolic partition across the width of the street. And, he may place a beam extending from here, from the other side of the house. According to Rabbi Yehuda, in that way, one is permitted to carry objects and place them in the area between the symbolic partitions, as he would in a private domain.

The Rabbis said to him: One may not place an eiruv in the public domain in that way. One who seeks to transform a public domain into a private domain must place actual partitions. Apparently, according to Rabbi Yehuda, the side posts function as partitions in the public domain, creating a private domain between the two houses. It follows from this that a side post is in fact deemed a proper partition, contrary to Rava’s statement.

The Gemara answers: This is not the reason behind Rabbi Yehuda’s statement. Rather, there Rabbi Yehuda holds that by Torah law two partitions suffice to constitute a private domain, and he requires side posts only as a conspicuous marker. Therefore, Rava’s position cannot be disproved from this source either.

Rav Yehuda said that Rav said: Unlike other alleyways, carrying within an alleyway whose length is equal to its width is not permitted by means of a side post of minimal width. Like a courtyard, carrying within it is permitted only by means of an upright board four handbreadths wide. Rav Ḥiyya bar Ashi said in the name of Rav: Carrying within an alleyway whose length is equal to its width is not permitted by a cross beam with the width of a handbreadth.

Rabbi Zeira said: How precise are the traditions of the Elders. He explains: Since the length of the alleyway is equal to its width, it is regarded like a courtyard, and carrying within a courtyard is not permitted by means of a side post or a cross beam, but only by means of an upright board of four handbreadths.

Rabbi Zeira said: Nonetheless, if this issue is difficult for me to understand, this is my difficulty: Let this side post be considered like an upright board of minimal width and permit carrying within the alleyway, just as an upright board permits carrying in a breached courtyard.

The Gemara explains that this is incorrect, as that which Rabbi Asi said that Rabbi Yoḥanan said escaped Rabbi Zeira’s attention: The upright boards of a courtyard must be four handbreadths wide, whereas a side post may be of minimal size.

Rav Naḥman said: We have a tradition that states: What is the type of alleyway in which carrying is permitted by means of a side post or a cross beam? Any alleyway whose length is greater than its width and has houses and courtyards opening into it. And what is the type of courtyard in which carrying is not permitted by means of a side post or a cross beam, but by an upright board of four handbreadths? Any courtyard that is square.

The Gemara wonders: If it is square, then yes, is it considered a courtyard? If it is round, no, is it not considered a courtyard? The Gemara makes a correction: This is what it is saying: If its length is greater than its width, it is considered an alleyway, and for an alleyway a side post or a cross beam suffices; but if its length is not greater than its width, i.e., it is square, it is considered a courtyard.

The Gemara asks: And by how much must its length exceed its width so that it can be considered an alleyway? Shmuel thought at first to say: It is not considered an alleyway unless its length is double its width, until Rav said to him: My uncle [ḥavivi], Rav Ḥiyya, said this: Even if its length is greater than its width by only a minimal amount, the halakhot of an alleyway apply to it.

We learned in the mishna: A certain disciple said before Rabbi Akiva in the name of Rabbi Yishmael, etc.