Rif Succah 9a {Succah 18a continues; 18b - 19a}

HIDE/SHOW IMAGE
9a

{Succah 18a continues}
with {metal} rods it is not a {good} reduction.

If in the roof {is the empty air} in the middle -- Rav Acha and Ravina argue about this.
One said that there is lavud in the middle, and the other said that there is no lavud in the middle.

And the halacha is that there is lavud, for we establish that throughout the entire Torah, {when there is a dispute between} Rav Acha and Ravina, Ravina is more lenient and the halacha is like him.

It was stated {by Amoraim}:
If he placed {schach} atop a balcony which has small pillars, all agree that it is valid. If it does not have small pillars:
Abaye said: It is valid.
And Rava said: It is invalid.

Abaye said: It is valid -- we say that the mouth {=edge} of the ceiling descends and closes.

{Succah 18b}
And Rava said: It is invalid -- we do not say that the mouth of the ceiling descends and closes.

And the halacha is like Rava.

And this that we say "atop a balcony" -- not literally on top of it, but rather next to it. {Thus, the roof of the balcony outside it descends and forms the missing wall.} As is written {Bemidbar 2:20}:

כ וְעָלָיו, מַטֵּה מְנַשֶּׁה; וְנָשִׂיא לִבְנֵי מְנַשֶּׁה, גַּמְלִיאֵל בֶּן-פְּדָהצוּר.

20 and next unto him shall be the tribe of Manasseh; the prince of the children of Manasseh being Gamaliel the son of Pedahzur,

and we translate {to Aramaic} "and those than encamp next to him" and this is its image:





{Bach has a better diagram:




}

{Succah 19a}
Rav Ashi found Rav Kahana placing schach upon a balcony that lacked small pillars.
He said to him: Does Master not hold that if it has smalls pillars it is valid; if it lacks small pillars it is invalid?
He showed him that it {a third wall of a handbreadths was visible from the outside {jutting out} and equal {and thus not visible} on the inside. And some say that it was visible from the inside and equal on the outside.