(Mishnah): (If Chatzeros, i.e. courtyards in front of houses, open to a Mavoy (alleyway that is open on one side to a public road), Chachamim forbid carrying in the Mavoy unless there is a Korah (horizontal beam) across the opening or a Lechi (vertical post) at one side of the opening. See Perush Chai diagram, Perek 1 number 1 in the English Charts section.) If [the Korah of] a Mavoy is more than 20 Amos above the ground, it must be lowered;

R. Yehudah says, it need not be lowered.

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

If it has Tzuras ha'Pesach (a Lechi on each side and a Korah on top of them), even if it is wider than 10, it need not be reduced.

(Gemara - R. Yosah, and R. Acha citing Rav): Rabanan learn [the maximum height of a Mavoy] from Pesach (the opening to) ha'Heichal. R. Yudah learns from Pesach ha'Ulam.

Question: If R. Yudah learns from Pesach ha'Ulam, he should allow only up to 40 Amos!

(Mishnah): Pesach ha'Ulam was 40 Amos tall and 20 Amos wide.

R. Chiya taught that [R. Yehudah is Machshir] even 40 or 50 Amos. Bar Kapara taught even 100 Amos!

Answer (R. Avin): R. Yehudah teaches like he taught elsewhere, and Rabanan teach like they taught elsewhere;

(Mishnah 9:5): Bridges [whose sides descend and make walls] Mefulashim, one may carry under them on Shabbos. R. Yehudah says so. Chachamim forbid.

Just like there, [R. Yehudah] views the edge [of the bridge, on each side] as if it descends and seals (makes a Mechitzah), also here (in a Mavuy), he views the Korah as if it descends and seals. (This is even if it is very high. Rabanan hold that a Korah is a Heker, so it must be visible. Up to 20 Amos it is visible.)

R. Yehudah's opinion about Sukah is like his opinion about Mavuy. (Just like he is Machshir a Korah above 20 Amos, he is Machshir Sechach above 20 Amos.) Rabanan's opinion about Sukah is like their opinion about Mavuy. (Just like they disqualify a Korah above 20 Amos, they disqualify Sechach above 20 Amos.)

Rejection: We find matters that are Kosher for Sukah and Pasul for Mavuy, and matters Kosher for Mavuy and Pasul for Sukah!

Difference #1: Dukranin (if Sechach was placed on poles, even though the walls are only 10 Tefachim tall and do not reach to the poles), it is Kosher for Sukah and Pasul for Mavuy (the Korah must rest on the walls of the Mavuy);

Support (Beraisa): If one brought four poles, and placed Sechach for a Sukah on them, it is Kosher for Sukah and Pasul for Mavuy.

Limitation #1: [It is Pasul for Mavuy] when it is three Tefachim higher than the walls of the Mavuy, but if it is not three Tefachim higher than the walls of the Mavuy, it is Kosher. (Also a Sukah is Pasul if the walls are three Tefachim above the ground!)

Limitation #2: [It is Pasul when it is three Tefachim higher than the walls -] this is when it is not four [Tefachim] wide. However, if it is four wide, even if it is very high [above the walls of the Mavuy], it is Kosher. (HA'GAON RAV C. KANIEVSKY, SHLITA - then Pi Tikra Yored v'Sosem applies, so it is considered a Mechitzah.)

Difference #2: [Two and a partial] walls are Kosher for Sukah, and Pasul for Mavuy!

Support (Beraisa): If two walls are proper (full walls, and they are adjacent), the third can be even a Tefach, and it is Kosher.

Strengthening of question (R. Chiyah citing R. Yochanan): If two walls are [even] four Tefachim each, and the third is even a Tefach, it is Kosher. A Mavuy is Pasul (one may not carry in it) unless it is closed on [all] four sides!

Difference #3: If [a breach in a wall] is wider than 10 Amos, it is Kosher for Sukah, and Pasul for Mavuy!

Difference #4: If one draped a vine or pumpkin tree over [a Sukah it is Pasul, and over a Mavuy it is Kosher]!

Difference #5: [Mechitzos permit a Mavuy only] up to Beis Sa'atayim, but more than Beis Sa'atayim, it is like a Mechitzah used to surround crops. One may carry only within four Amos [but it is Kosher for Sukah]!

Difference #6: If it has more shade than sun, it is Pasul for Sukah, and for a Mavuy it is Kosher!

Difference #7: A Sukah roofed [with beams] is Pasul, and a roofed Mavuy is Kosher [even without a Lechi or Korah - PNEI MEIR, HA'GAON RAV C. KANIEVSKY, SHLITA]!

(R. Ami citing R. Hoshayah): This is not only if it is [fully] roofed. Rather, even if he put on it a plank and it is four wide, it permits the Mavuy [even if it is not Kosher for a Korah, e.g. it is above 20 Amos].