(Mishnah): A Sukah that is taller than twenty Amos is invalid.

R. Yehuda says that it is valid.

If it is not ten Tefachim tall, if it does not have three walls, or if it provides more sun than shade - in any of these cases it is invalid.

(Gemara): R. Yosi taught the following statement without stating that it was in the name of Rav.

But R. Acha quoted Rav as saying - Rabbanan learned the measurement (that the maximum height of a Sukah is 20 Amos) from the entrance of the Heichal (the Sanctuary of the Temple)

R. Yehuda learned his measurement (that if the Sukah is taller than 20 Amos it is valid) from the entrance of the Ulam (the entrance hall of the Temple).

Question: If he learns his opinion from the entrance of the Ulam, he should also limit the maximum height to forty Amos, as the Mishnah in Maseches Midos teaches -

The entrance of the Ulam was forty Amos tall and twenty Amos wide...?

R. Chiya taught in a Beraisa that it is valid even if it is fifty Amos tall. Bar Kafra taught in a Beraisa that it is valid even if it is one hundred Amos tall.

Answer (R. Avin): R. Yehuda follows his reasoning and Rabbanan follow their reasoning, as the Mishnah in Maseches Eiruvin teaches -

R. Yehuda says - And similarly, bridges underneath which a road passes (that have walls underneath on either side) - one may carry underneath them on Shabbos.

The Chachamim prohibit it.

Just as R. Yehuda says there that we view the roof as if it descends like walls, so too here, we view the bar as if it descends and encloses.

R. Yehuda holds the same view in the laws of Sukah and in the laws of Mavoi (the beam across the entrance to an alleyway that permits carrying inside it). Rabbanan also hold the same view in the laws of Sukah and in the laws of Mavoi.

Question: But they are not the same, as there are things that qualify for a Sukah but not for a Mavoi and vice-versa.

Forked canes are valid for Sukah and invalid for a Mavoi, as the Beraisa teaches - If a person brought four forked canes and rested Schach on top of them, the Sukah is valid but a Mavoi would be invalid (if he rested the beam on top of canes above the walls of the Mavoi)...?

Answer: They are only invalid in a Mavoi if they are three Tefachim above the Mavoi's wall but if not, they are valid. Furthermore, they are only invalid if they are not four Tefachim wide but if they are, they would be valid even if they arevery high.

Question: There are walls that are valid for a Sukah but invalid for a Mavoi, as the Beraisa teaches -

(Difference #1) Two must be full walls and the third can be only a Tefach.

Strengthening the Question (R. Chiya quoting R. Yochanan): The two walls could even be four Tefachim long and the third a Tefach but a Mavoi must be closed on all four sides...?

(Difference #2) A Sukah that is wider than ten Amos is valid but a Mavoi (entrance) is invalid...?

(Difference #3) If he stretched up a vine branch or a pumpkin or creeper branch and used it as Schach on a Sukah, it is invalid; but if a Mavoi was covered with these branches, it does not require any further changes to validate it...?

(Answer to #3) This only applies to an area as big as a Beis Sasayim, but bigger than that becomes like a fence that was surrounding seeds, that one may only carry within four Amos.

(Difference #4) A Sukah that has more sun than shade is invalid, but a Mavoi would be valid....?

(Difference #5) A covered Sukah is invalid but a Mavoi is valid...?

(R. Acha quoting R. Hoshiya) Not only if it was covered is the Mavoi valid, but even if he put a bar there that was four Tefachim wide, it permits carrying in the Mavoi.