Answer: The Beraisa is like Rebbi, who requires two remnants (one on each side of a totally breached wall):

(Beraisa): One remnant permits a Chatzer;

Rebbi says, two remnants permit.

Question: We understand this if Nir'eh miba'Chutz v'Shavah mibi'Fnim is not considered a Lechi:

Rebbi holds like R. Yosi (who requires a Lechi [and all the more so a remnant] to be at least three Tefachim (14b)). Ravina is wrong (if the small Chatzer is not centered, it is less than three Tefachim from one side, that remnant is too small to permit the big Chatzer) and R. Zeira is wrong. (If the small Chatzer jut into the big Chatzer, since it must be centered, the sides are Lavud, and they would permit the small Chatzer);

The big Chatzer must be an Amah bigger than the small Chatzer [to allow a remnant of three Tefachim on each side].

However, if Nir'eh miba'Chutz v'Shavah mibi'Fnim is considered a Lechi, R. Zeira and Ravina are correct, and Rebbi argues with R. Yosi, why do we establish the big Chatzer to be 11? To permit the big Chatzer, it could exceed 10 by a mere two Tefachim (Tosfos - perhaps any amount)!

If we make it bigger to teach that the small Chatzer is forbidden, we should teach that it is more than 11 [so that this will always be true. When it is 11, it is not true if it is centered, for both sides are Lavud to the walls of the big Chatzer]! (Even when it is more than 11, we must assume that the walls are not overly thick - if not, it is always possible that they are within three on both sides - PF.)

Conclusion: We must say that Nir'eh miba'Chutz v'Shavah mibi'Fnim is not considered a Lechi.

Rav Yosef: I never heard this teaching. (Presumably, this was after he forgot his learning.)

Abaye: You taught it to us, regarding the following teaching!

(Rami bar Aba): If a Lechi is just outside the Mavoy wall and [seemingly] extends the wall:

If it is less than four Amos, it is considered a Lechi, so one may carry until its inner edge;

If it is four Amos [or more], it is considered a Mavoy, and not a Lechi. One may not carry in the Mavoy.

(Rav Yosef): We learn three things from this:

Bein ha'Lechayayim is forbidden (one may not carry past the inner edge);

The extent of a Mavoy is four Amos;

Nir'eh miba'Chutz v'Shavah mibi'Fnim is considered a Lechi.

The Halachah is, Nir'eh miba'Chutz v'Shavah mibi'Fnim is considered a Lechi.

Question: Above (b), we refuted this. How can we say that it is the Halachah?!

Answer: (Tana'im argue about this.) Beraisa #1 (9b) considers it a Lechi.

(Mishnah): If [the opening of the Mavoy] is wider than 10 Amos, it must be reduced [through a Mechitzah in the middle];

(Beraisa): If it is wider than 10 Amos, it must be reduced;

R. Yehudah says, it need not be reduced.

Question (Abaye): How wide does R. Yehudah permit?

Answer #1 (Rav Achi): He permits up to 13 and a third Amos. There is a Kal va'Chomer from Pasei Bira'os (planks surrounding a well, which permit carrying inside - 17b):

Pasei Bira'os permit even if Parutz Merubah Al ha'Omed (there is more empty space than wall), yet they do not permit a gap more than 13 and a third. Parutz Merubah Al ha'Omed [in all four walls together] forbids a Mavoy. All the more so a gap of more than 13 and a third forbids!

Rejection #1: Just the contrary! Because we are lenient to allow Parutz Merubah Al ha'Omed regarding Pasei Bira'os, we do not allow [a gap of more than] 13 and a third. Since we are stringent to require Omed Merubah Al ha'Parutz for a Mavoy, we can permit more!

Rejection #2: Regarding Pasei Bira'os, just like we are lenient to allow Parutz Merubah Al ha'Omed, we allow [a gap of] up to 13 and a third. Regarding a Mavoy, we are stringent to require Omed Merubah Al ha'Parutz, and we allow only up to 10 Amos!

(Levi - Beraisa): If [the opening of] a Mavoy is 20 Amos wide, it suffices to stick a stick in the middle (less than 10 Amos remains on each side).

(Levi): The Halachah is not like this Beraisa (the air on both sides of the stick is Mevatel it).

Question: How can one permit it?

Answer #1 (Shmuel citing Levi): One erects a plank 10 Tefachim tall and four Amos long, extending [from the middle of the opening] into the Mavoy. (Since it has a Shi'ur Mavoy, it is not Batel.)

Answer #2: We can do like Rav Yehudah [and put planks along the opening]:

(Rav Yehudah): If a Mavoy is 15 Amos wide, one takes a plank three Amos wide and puts it two Amos from a wall (it is more than the air on that side, therefore it is not Batel. Rav Yehudah discusses an opening 15 Amos wide. If the opening is 20, two planks or a thicker plank is required.)

Question: [In Rav Yehudah's case] why don't we erect two planks, each one and a half Amos wide with two Amos in between! (Tosfos - this would be better, for it looks more like an opening. Rashi - we ask why one must seal off three Amos together. It should suffice to erect two planks like this!)

Answer #1: We must say that 'Omed Merubah Al ha'Parutz from two sides' (the plank on either side is smaller than the gap, but together they are bigger than it) is not considered Omed [Merubah Al ha'Parutz, i.e. it is invalid]!

Rejection (and Answer #2): Really, 'Omed Merubah from two sides' is considered Omed. Here is different, because the air from both sides [of the plank away from the wall] is Mevatel it.

Question: Why don't we erect three planks, each one Amah wide, with an Amah between planks!

Answer #1: We must say that Omed k'Parutz (Mechitzos that are as wide as the space between them) does not permit!

Rejection (and Answer #2): Really, Omed k'Parutz permits. Here is different, because the air from both sides [of the plank in the middle] is Mevatel it.

Question: Why don't we leave an Amah empty from the wall, erect a plank one and a half Amos wide, leave an Amah and erect another plank of one and a half!

Answer: Indeed, also that permits. Chachamim did not exert one to do so.

Question: Perhaps people will use the small opening and abandon the large opening! (The latter would no longer be considered the opening of the Mavoy, so its Lechi cannot permit the Mavoy)!

Answer (Rav Ada bar Masnah): There is a Chazakah [of human nature], that one does not abandon a large opening and use a small opening.

Question: What is the difference between this and the case of R. Ami and R. Asi? (If part of a side wall of a Mavoy near the opening was broken, and less than four Tefachim of the wall remain [by the opening], it does not permit a Pirtzah of three Tefachim, lest the Pirtzah become the primary opening. This would invalidate the Lechi or Korah in the original opening.)

Answer: There, the new opening is a shortcut (it is in a different direction). Here, it is not.

(Beraisa): Hide of Asla (this will be explained) and its hole join to the Shi'ur of a Tefach [to be an Ohel regarding Tum'as Mes].

Question: What is this?

Answer (Rabah bar bar Chanah): It is a toilet seat.

Question: How big can the hole be?

Answer #1 (Rav Dimi): It can be [up to] two fingers, surrounded by two fingers [of hide] on each side.

Answer #2 (Ravin): It can be [up to] one finger, surrounded by one and a half fingers on each side.

Abaye (to Rav Dimi): Do you argue with Ravin?

Rav Dimi: We do not argue. I discuss pinkies, and he discusses thumbs (a Tefach equals six pinkies, which equals four thumbs.

Abaye: You do argue! You hold that Omed Merubah from two sides is Omed, and he disagrees! (This is why he requires each side to be bigger than the hole.)

If you did not argue, Ravin should have said that the hole is one and a third fingers (one and a third thumbs equals two pinkies), surrounded by one and a third fingers on each side!

Rav Dimi: If we argued [and I permit Omed Merubah from two sides], I should have said that the hole is [bigger than each side, e.g.] two and two thirds fingers, surrounded by one and two thirds fingers on each side!

Rav Dimi: Rather, you can say that we argue about Parutz k'Omed (from one side. I permit, and he forbids.)