Category: Eruvin

Sugya: נראה בפנים ואינו נראה מבחוץ and נראה מבחוץ ואינו נראה מבפנים 

Review the גמרא דף ט: “ור’ יוחנן (eighteen lines from the top of the Amud) until “דף י. “האי  ” (second line from top of the Amud)

Question:

Is the machlokes whether נראה מבחוץ  is a valid Lechi dependent on the argument whether the היכר is for the people outside the Mavui or inside the Mavui? 

See גאון יעקב 

https://hebrewbooks.org/pdfpager.aspx?req=14053&st=&pgnum=52

And ר’ יהונתן “מה שנראה מבפנים 

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=329

See רש”י דף ח. “נראה מבחוץ 

Note: the discussion is not about a Lechi but rather about creating a פתח – door

See the קהילת יעקב עירובין סוף ס’ ה who brings a major chidush from the תורת רפאל in the concept of Lechi in regards to נראה מבחוץ ואינו נראה מבפנים 

What exactly does נראה מבחוץ ואינו נראה מבפנים look like?

Rashi gives two different pictures 

See רש”י דף ט: “נראה מבחוץ 

See רש”י דף ט: “כותל שצדו אחד

Learn תוס’ “כותל 

Tosfos asks why did Rashi give a different image of נראה מבחוץ 

Learn מהרש”א “קשה

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=265

Learn גמרא סוכה דף יט. “רב אשי אשכחיה (thirteen lines from top of the Amud) until the two dots

https://hebrewbooks.org/shas.aspx?mesechta=7&daf=19&format=pdf

Learn תוס’ “אחוי who asks two questions on how can a Lechi be used to create a third wall for Sukkah.

Learn רא”ש ס’ לד “רב אשי who elaborates on the questions of Tosfos and gives an answer

https://hebrewbooks.org/pdfpager.aspx?req=14319&st=&pgnum=474

Sugya: נראה בפנים ואינו נראה מבחוץ and נראה מבחוץ ואינו נראה מבפנים 

Review the גמרא דף ט: “ור’ יוחנן (eighteen lines from the top of the Amud) until “דף י. “האי  ” (second line from top of the Amud)

Major Question:

How could a Lechi be created through Lavud when there is no post that is noticable? 

Note: in Sugya of מבוי שרצפו בלחיים Rav Ashi said we view many individual Lechi as one wide Lechi through Lavud. 

Question:

Is the machlokes whether נראה מבחוץ  is a valid Lechi dependent on the argument whether the היכר is for the people outside the Mavui or inside the Mavui? 

See גאון יעקב 

https://hebrewbooks.org/pdfpager.aspx?req=14053&st=&pgnum=52

And ר’ יהונתן “מה שנראה מבפנים 

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=329

See רש”י דף ח. “נראה מבחוץ 

Note: the discussion is not about a Lechi but rather about creating a פתח – door

See the קהילת יעקב עירובין סוף ס’ ה who brings a major chidush from the תורת רפאל in the concept of Lechi in regards to נראה מבחוץ ואינו נראה מבפנים 

Learn גמרא סוכה דף יט. “רב אשי אשכחיה (thirteen lines from top of the Amud) until the two dots 

Learn תוס’ “אחוי who asks two questions on how can a Lechi be used to create a third wall for Sukkah.

Learn רא”ש ס’ לד “רב אשי who elaborates on the questions of Tosfos and gives an answer 

Quickly review תוס’ דף ט: “ולרשב”ג 

Review מהרש”א

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=265

Major Question:

According to the opinion לחי משום מחיצה and חודו חיצון סותם (we consider the outer face plate of the Lechi as closing the area). How could the Lechi partially protruding outside the Mavui permit one to carry in the Mavui as there is no wall opposite the Lechi for the Lechi to connect to?

See ב’ גר”א או”ח ס’ שס”ג סע’ יג

https://hebrewbooks.org/pdfpager.aspx?req=14325&st=&pgnum=232

Sugya: נראה בפנים ואינו נראה מבחוץ and נראה מבחוץ ואינו נראה מבפנים 

Very quickly review גמרא דף ט: “ולרבי שמעון בן גמליאל  (sixth line from top of the Amud) until ור’ יוחנן (eighteen lines from the top of the Amud)

Review תוס’ דף ט: “ולרשב”ג 

Tosfos asks on Rashi how could the protruding Lechi permit people to carry opposite the Lechi? This area is Reshus Harabim? 

Question on Tosfos:

It seems that Tosfos understands why the Lechi permits one to carry inside the Mavui. This seems to be contradictory to the Gemara on bottom of דף ח עמוד ב which says a Korah placed outside the walls of a Mavui is invalid. So how could a Lechi placed outside the Mavui permit one to carry inside the Mavui? 

Learn מהרש”א

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=265

What is the explanation of the מהרש”א?

Learn חזון איש מועד ס’ ס”ז אות י”ז

https://hebrewbooks.org/pdfpager.aspx?req=14336&st=&pgnum=212

https://hebrewbooks.org/pdfpager.aspx?req=14336&st=&pgnum=213

Major Question:

According to the opinion לחי משום מחיצה and חודו חיצון סותם (we consider the outer face plate of the Lechi as closing the area). How could the Lechi partially protruding outside the Mavui permit one to carry in the Mavui as there is no wall opposite the Lechi for the Lechi to connect to?

See ב’ גר”א או”ח ס’ שס”ג סע’ יג

https://hebrewbooks.org/pdfpager.aspx?req=14325&st=&pgnum=232

Continue learning the גמרא דף ט: “ור’ יוחנן (eighteen lines from the top of the Amud) until “ולימא ” (last line – bottom of the Amud)

Major Question:

How could a Lechi be created through Lavud when there is no post that is noticable? 

Learn תוס’ “כותל

Clarify what the case of נראה בפנים ואינו נראה מבחוץ and נראה מבחוץ ואינו נראה מבפנים looks like. 

Sugya: נראה בפנים ואינו נראה מבחוץ and נראה מבחוץ ואינו נראה מבפנים 

Review גמרא דף ט: “ולרבי שמעון בן גמליאל  (sixth line from top of the Amud) until ור’ יוחנן (eighteen lines from the top of the Amud)

Clarify what the case of נראה בפנים ואינו נראה מבחוץ and נראה מבחוץ ואינו נראה מבפנים looks like. 

Learn תוס’ דף ט: “ולרשב”ג 

Tosfos asks on Rashi how could the protruding Lechi permit people to carry opposite the Lechi? This area is Reshus Harabim? 

Question on Tosfos:

It seems that Tosfos understands why the Lechi permits one to carry inside the Mavui. This seems to be contradictory to the Gemara on bottom of דף ח עמוד ב which says a Korah placed outside the walls of a Mavui is invalid. So how could a Lechi placed outside the Mavui permit one to carry inside the Mavui? 

Learn מהרש”א

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=265

What is the explanation of the מהרש”א?

Learn חזון איש מועד ס’ ס”ז אות י”ז

https://hebrewbooks.org/pdfpager.aspx?req=14336&st=&pgnum=213

Major Question:

According to the opinion לחי משום מחיצה and חודו חיצון סותם (we consider the outer face plate of the Lechi as closing the area). How could the Lechi partially protruding outside the Mavui permit one to carry in the Mavui as there is no wall opposite the Lechi for the Lechi to connect to?

See ב’ גר”א או”ח ס’ שס”ג סע’ יג

https://hebrewbooks.org/pdfpager.aspx?req=14325&st=&pgnum=232

Continue learning the גמרא דף ט: “ור’ יוחנן (eighteen lines from the top of the Amud) until “אמר רבה בר רב הונא” (twelve lines from bottom of the Amud)

Sugya: נראה בפנים ואינו נראה מבחוץ and נראה מבחוץ ואינו נראה מבפנים 

To start the next gemara /Sugya quickly review the גמרא דף ט.”א’ל רב הונא בריה דרבי יהושע (twelve lines from bottom of the Amud) until “דף ט: “ולרבי שמעון בן גמליאל  (sixth line from top of the Amud) 

Learn “גמרא דף ט: “ולרבי שמעון בן גמליאל  (sixth line from top of the Amud) until ור’ יוחנן (eighteen lines from the top of the Amud)

Clarify what the case of נראה בפנים ואינו נראה מבחוץ and נראה מבחוץ ואינו נראה מבפנים looks like. 

Learn “תוס’ דף ט: “ולרשב”ג 

Tosfos asks on Rashi how could the protruding Lechi permit people to carry opposite the Lechi? This area is Reshus Harabim? 

Question on Tosfos:

It seems that Tosfos understands why the Lechi permits one to carry inside the Mavui. This seems to be contradictory to the Gemara on bottom of דף ח עמוד ב which says a Korah placed outside the walls of a Mavui is invalid. So how could a Lechi placed outside the Mavui permit one to carry inside the Mavui? 

Learn מהרש”א 

Conclusion of Sugya: תחת הקורה & בין הלחיים  

Quickly review the ריף 

And the בעל המאור who disagrees with the Rif

Learn the מלחמת ה who defends the conclusion of the Rif

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=329

In conclusion what is the reason

Of אביי that says בין לחיים אסור?

Of רבא that says it’s מותר?

How do we conclude l’halacha?

Learn שולחן ארוך או”ח ס’ שס”ה סע’ ד with the משנה ברורה and ביאור הלכה

https://hebrewbooks.org/pdfpager.aspx?req=60389&st=&pgnum=74

https://hebrewbooks.org/pdfpager.aspx?req=60389&st=&pgnum=75

Very quickly review the גמרא דף ט.”א’ל רב הונא בריה דרבי יהושע (twelve lines from bottom of the Amud) until דף ט: “ולרבי שמעון בן גמליאל  (sixth line from top of the Amud) 

Is the reason for אביי connected to his opinion that Lechi is a mechitza?

Learn the ריף 

Note: the requirements that the Rif specifies to allow one to carry between the Lechi.  

Learn the בעל המאור who disagrees with the Rif

Learn the מלחמת ה who defends the conclusion of the Rif

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=329

In conclusion what is the reason

That אביי says בין לחיים אסור 

That רבא says it’s מותר

Very quickly review the גמרא דף ט.”תני ר’ זכאי (fourteen lines from top of the Amud) until “א’ל רב הונא בריה דרבי יהושע (twelve lines from bottom of the Amud) 

Continue learning the Gemara until דף ט: “ולרבי שמעון בן גמליאל  (sixth line from top of the Amud) 

Last week wwe discussed the following question. 

Rava says the area בין לחיים is compared to מקום שאין בו ד על ד and it’s permitted for both the people in Reshus Hayachid and Reshus Harabim to use. 

How could the people in Reshus Harabim use this area that is between three walls, it’s a Reshus Hayachid?

The רשב”א “מקום answers we only consider the area between the Lechi annexed to the Mavui  

https://hebrewbooks.org/pdfpager.aspx?req=37275&st=&pgnum=12

Learn חידושי מאירי דף ט. “אמר רבא who says similar to the רשב”א 

Note the reason the מאירי gives as to why this is so.  

What is the reason of אביי why בין לחיים אסור? 

Learn חידושי מאירי דף ט. “ואביי דאמר  

Is the reason of אביי connected to his opinion that Lechi is a mechitza?

Learn the ריף 

Note: the requirements that the Rif specifies to allow one to carry between the Lechi.  

Learn the בעל המאור who disagrees with the Rif

Learn the מלחמת ה who defends the conclusion of the Rif

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=329

Learn תוס’ דף ח: “הכל 

In conclusion what is the reason

That אביי says בין לחיים אסור 

That רבא says it’s מותר

Is the reason Tosfos presents the same as our gemara presents? 

Review the גמרא דף ט.”תני ר’ זכאי (fourteen lines from top of the Amud) until “א’ל רב הונא בריה דרבי יהושע (twelve lines from bottom of the Amud) 

Clarify the different opinions the gemara lists in regards to carrying underneath the Korah and carrying between the Lechi.

Questions:

Rava says the area בין לחיים is compared to מקום שאין בו ד על ד and it’s permitted for both the people in Reshus Hayachid and Reshus Harabim to use. 

How could the people in Reshus Harabim use this area that is between three walls, it’s a Reshus Hayachid?

Learn רשב”א “מקום

https://hebrewbooks.org/pdfpager.aspx?req=37275&st=&pgnum=12

And ריטב”א “ורבא

https://hebrewbooks.org/pdfpager.aspx?req=37287&st=&pgnum=14

What is the reason of אביי why בין לחיים אסור? 

Is the reason of אביי connected to his opinion that Lechi is a mechitza?

Learn בעל המאור and מלחמת ה 

https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=329

Learn תוס’ דף ח: “הכל 

Is the reason Tosfos presents the same as our gemara presents? 

Learn the גמרא דף ט.”תני ר’ זכאי (fourteen lines from top of the Amud) until “א’ל רב הונא בריה דרבי יהושע (twelve lines from bottom of the Amud) 

Clarify the different opinions the gemara lists in regards to carrying underneath the Korah and carrying between the Lechi.

Question:

What is the reason of אביי why בין לחיים אסור? 

See תוס’ דף ח: “הכל 

Is the reason Tosfos presents the same as our gemara presents? 

Conclusion of Sugya: חבוט ולבוד

Very quickly review the גמרא דף ט. “רב אשי אמר (nine lines from top of the Amud) until “תני ר’ זכאי (fourteen lines from top of the Amud)  

The ר”ן סוכה דף ט. דפי הריף (few lines before דברי המתחיל “איתמר) says we can not combine the two halachick concepts of דופן עקומה and לבוד.

https://hebrewbooks.org/pdfpager.aspx?req=14319&st=&pgnum=600

Major Question:

According to the Ran how can we combine Lavud and Chavut in our case of the Gemara?

(Extra- see שו”ת רע”א ח”א ס’ יב who answers this question)

https://hebrewbooks.org/pdfpager.aspx?req=1161&pgnum=20

The Ritva & Rashba clearly established the case of our gemara is where the diagonal line from the wall of the Mavui to the Korah is three tefachim or more. 

Is there a possible explanation as to why both concepts of חבוט and לבוד are needed to connect the Korah to the walls of the Mavui even when the diagonal is less than three?

Learn ח’ ר’ חיים ה’ סוכה פרק ה הלכה כא (attached in this email – starting from paragraph on bottom of right column) 

Note how Reb Chaim explains

1) Why Chavut and Lavud is needed even though the diagnol line between the Korah and the walls of the Mavui is less then three?

2) A new answer to question of Tosfos as to why the Korah can not be higher then three tefachim as Chavut is not limited to within three tefachim. 

3) Whether the shapes of the pegs holding up the Korah make a difference 

Learn the גמרא דף ט.”תני ר’ זכאי (fourteen lines from top of the Amud) until “א’ל רב הונא בריה דרבי יהושע (twelve lines from bottom of the Amud) 

https://images.shulcloud.com/13521/uploads/YNB-PTI/shiurim/rabbibodenheim/ravchaimeruvn9a.jpg

Review the גמרא דף ט. “רב אשי אמר (none lines from top of the Amud) until “תני ר’ זכאי (fourteen lines from top of the Amud)  

Learn תוס’ דף ט. “שאין who asks why is it necessary for the Korah to be within the height of 3 tefachim of the wall in order to say חבוט when it is clear from the gemara Sukkah that the concept of חבוט is not limited like לבוד to 3 tefachim. 

Questions:

Why do we need both concepts of חבוט and לבוד to connect the Korah to the walls of the Mavui.  Why can’t we consider the Korah connected through לבוד alone?

What is the shape of the pegs that are holding up the Korah?

Learn ריטב”א “כגון שאין בגובהן ג’ טפחים 

https://hebrewbooks.org/pdfpager.aspx?req=37287&st=&pgnum=14

Note how the Ritva answers the above questions. See the answer the Ritva gives to Tosfos question. 

Learn רשב”א דף ט. “מהו דתימא and רשב”א דף ח: “לדברי המתיר  

https://hebrewbooks.org/pdfpager.aspx?req=37275&st=&pgnum=11&hilite=

https://hebrewbooks.org/pdfpager.aspx?req=37275&st=&pgnum=12

Rashi on bottom of דף ח עמוד ב said Lavud can not be applied to connect something to a halchachik wall.

Does that apply to Chavut as well? 

See ר”ן סוכה דף ט. דפי הריף (few lines before דברי המתחיל “איתמר)  Who says we can not combine the two halachick concepts of דופן עקומה and לבוד.

https://hebrewbooks.org/pdfpager.aspx?req=14319&st=&pgnum=600

See שו”ת רע”א ח”א ס’ יב who discusses this and how we can combine Lavud and Chavut in our case of the Gemara 

https://hebrewbooks.org/pdfpager.aspx?req=1161&pgnum=20

See ח’ ר’ חיים ה’ סוכה פרק ה הלכה כא who explains the opinion of the Rambam and how it differs from Tosfos and how the Rambam explains the configuration of the pegs holding up the Korah.  

Zoom link for those who can not attend live.

Same zoom link for the entire morning

https://us02web.zoom.us/j/98313738910?pwd=S0NzYThFSG01S05KcTEybmxrY2JGZz09

Quickly review the גמרא דף ח: בעי מיניה רמי בר חמא (four lines from bottom of the Amud) until “איתיביה” (bottom of the Amud)

Continue learning the גמרא דף ח: “איתיביה until דף ט. “רב אשי אמר (nine lines from top of the Amud) 

Question:

Is רב אדא בר מתנה asking only on Rava who rules the Korah needs to be resting on top of the walls of the Mavui or also on Rav Chisda who rules according to opinion of קורה משום מחיצה the inner face plate of the Korah needs to be flush to the walls of the Mavui?

See תוס’ ישנים (on side of the Gemara) 

See ח’ ר”ן

Continue learning the גמרא דף ט. “רב אשי אמר until “תני ר’ זכאי (fourteen lines from top of the Amud)  

Learn תוס’ דף ט. “שאין who asks why is it necessary for the Korah to be within the height of 3 tefachim of the wall in order to say חבוט when it is clear from the gemara Sukkah that the concept of חבוט is not limited like לבוד to 3 tefachim. 

Questions:

Why do we need both concepts of חבוט and לבוד to connect the Korah to the walls of the Mavui.  Why can’t we consider the Korah connected through לבוד alone?

What is the shape of the pegs that are holding up the Korah?

Learn ריטב”א “כגון שאין בגובהן ג’ טפחים 

Note how the Ritva answers the above questions. See the answer the Ritva gives to Tosfos question. 

Learn רשב”א דף ט. “מהו דתימא and רשב”א דף ח: “לדברי המתיר  

Learn the גמרא דף ח: בעי מיניה רמי בר חמא ((four lines from bottom of the Amud) until “איתיביה” (bottom of the Amud)

Question:

Is Rav Chisda saying his ruling according to the reasoning of קורה משום מחיצה or קורה משום היכר?

Bring a proof from Rashi

Learn ריטב”א

Rashi “דף ח: “לדברי המתיר says the closure created by the outer face plate of the Korah is not connected to the Mavui. 

Question:

Why can’t we consider it connected to the Mavui through the concept of Lavud? 

Learn רשב”א

Learn the גמרא דף ח: “איתיביה until דף ט. “רב אשי אמר (nine lines from top of the Amud) 

Question:

Is רב אדא בר מתנה asking only on Rava who rules the Korah needs to be resting on top of the walls of the Mavui or also on Rav Chisda who rules according to opinion of קורה משום מחיצה the inner face plate of the Korah needs to be flush to the walls of the Mavui?

See תוס’ ישנים (on side of the Gemara) 

See ח’ ר”ן

Continue learning the גמרא דף ט. “רב אשי אמר until “תני ר’ זכאי (fourteen lines from top of the Amud)  

Learn תוס’ דף ט. “שאין 

Questions:

Why do we need both concepts of חבוט and לבוד to connect the Korah to the walls of the Mavui.  Why can’t we consider the Korah connected through לבוד alone?

What is the shape of the pegs that are holding up the Korah?

Learn רשב”א 

Learn the גמרא דף ח:  “איבעיא להו מהו להשתמש תחת הקורה until “איתיביה (bottom of the Amud)

Question:

Why is it definitely prohibited to carry in the area opposite the Lechi?

Learn תוס’ “הכל (first half of Tosfos until “דהא אביי )

The Rishonim give other explanations.

Learn רשב”א דף ח: “אמר רב חסדא

https://hebrewbooks.org/pdfpager.aspx?req=37275&st=&pgnum=11&hilite=

Learn תוס’ רי”ד דף ט for a chiddush in how Lechi operates as a Mechitza

(See attachment)

Learn קרן אורה דף ט. “תני ר’ זכאי who adds an understanding in the operation of Lechi as a Mechitza 

Learn ח’ ר”ן

Rashi “לדברי המתיר says the closure created by the outer face plate of the Korah is not connected to the Mavui. 

Question:

Why can’t we consider it connected to the Mavui through the concept of Lavud? 

See רשב”א

Continue learning the גמרא דף ח: איתיביה until “תני ר’ זכאי” (twelve lines from top of the Amud)

Conclusion of Sugya קורה באלכסון

Quickly review the גמרא דף ח: “אמר רב כהנא בר תחליפא” until “איבעיא להו מהו להשתמש תחת הקורה

Review תוס’ “מניח

Questions:

Tosfos gives two answers. 

What’s the difference between the two answers?

Learn ריטב”א – note how he answers Tosfos question. 

https://hebrewbooks.org/pdfpager.aspx?req=37287&st=&pgnum=13

What is the difference between Tosfos and the Ritva answers?

Rava holds the Korah must be placed straight and not on an angle because a Korah is just considered a היכר and placing a Korah on an angle is not a היכר.

Major Question: 

Tosfos תוס’ “מניח asked according to Rav Kahana how could it be permitted to carry along the border of the Korah even opposite the long wall as there are only two walls blocking in this part of the Mavui and need minimum of three walls to make it a reshus hayachid. Tosfos first answer is according to Rav Kahana Korah is Mechitza and therefore there really are three walls. 

Rava explains his position that one must place the Korah on straight from the edge of the short wall and parallel to the opposite wall to the edge of the long wall because  קורה משום היכר and if place the Korah on an angle its not a היכר 

Why doesn’t Rava just simply say the reason is קורה משום היכר and therefore if place the Korah on an angle from the short side to the long side you will only have two walls? 

According to Rava if one places the Korah on an angle from the edge of the short wall to the edge of the long wall would it be permitted to carry in the back part of the Mavui from the inside of the short wall? 

See ביאור הלכה ס’ שס”ג סע’ ל “אינו מניח who brings a dispute between the Machatzits Hashekel and Pri Megadim regarding this.

https://hebrewbooks.org/pdfpager.aspx?req=60389&st=&pgnum=66

See מחצית השקל ס’ שס”ג ס”ק ל for his Chidush and the פרי מגדים משבצות זהב ס”ק כא who argues and based on his position answers the major question we asked above. 

Major Question:

How could the Machatzitz Hashekel permit carrying in the back part of the Mavui Tosfos clearly says if one can not carry opposite the long wall than its considered outside the mavui and the korah is considered placed outside the mavui therefore the Korah should not be able to allow one to carry inside any part of the mavui? 

Learn the גמרא דף ח:  “איבעיא להו מהו להשתמש תחת הקורה until “איתיביה (bottom of the Amud)

Question:

Why is it definitely prohibited to carry in the area opposite the Lechi?

Learn תוס’ “הכל (first half of Tosfos until “דהא אביי )

The Rishonim give other explanations.

Learn רשב”א דף ח: “אמר רב חסדא

Learn תוס’ ריד דף ט for a chidush in how Lechi operates as a Mechitza 

Learn קרן אורה דף ט. “תני ר’ זכאי who adds an understanding in the operation of Lechi as a Mechitza 

Quickly review the גמרא דף ח: “אמר רב כהנא בר תחליפא” until “איבעיא להו מהו להשתמש תחת הקורה

Review תוס’ “מניח

Questions:

Tosfos gives two answers. 

What’s the difference between the two answers?

Learn ריטב”א – note how he answers Tosfos question. 

https://hebrewbooks.org/pdfpager.aspx?req=37287&st=&pgnum=13

What is the difference between Tosfos and the Ritva answers?

Rava argues and holds the Korah must be placed straight and not on an angle. The gemara says the reason is because a Korah on an angle is not a היכר.

Why doesn’t the gemara simply say the reason is קורה משום היכר and therefore if place the Korah on an angle from the short side to the long side you will only have two walls? 

See ביאור הלכה ס’ שס”ג סע’ ל “אינו מניח

https://hebrewbooks.org/pdfpager.aspx?req=60389&st=&pgnum=66

See מחצית השקל ס’ שס”ג ס”ק ל and פרי מגדים משבצות זהב ס”ק כא

Can one place a Korah on an angle if it’s placed in middle of the mavui? 

See רא”ש ס’ י (first half)

And קרבן נתנאל אות ע

And שולחן ארוך או”ח ס’ שס”ג, ל

Continue learning the גמרא דף ח:  “איבעיא להו מהו להשתמש תחת הקורה until “איתיביה (bottom of the Amud)

Learn the גמרא דף ח: “אמר רב כהנא בר תחליפא” until “איבעיא להו מהו להשתמש תחת הקורה

Learn תוס’ “מניח

Questions:

Why does Rashi and Tosfos both explain according to רב כהנא it is permitted to carry opposite the long wall?

In the question of Tosfos why does tosfos understand it’s considered as there are only two walls ?

Tosfos gives two answers. 

What’s the difference between the two answers?

Learn ריטב”א – note how he answers Tosfos question. 

https://hebrewbooks.org/pdfpager.aspx?req=37287&st=&pgnum=13

What is the difference between Tosfos and the Ritva answers?

Rava argues and holds the Korah must be placed straight and not on an angle. The gemara says the reason is because a Korah on an angle is not a היכר.

Why doesn’t the gemara simply say the reason is קורה משום היכר and therefore if place the Korah on an angle from the short side to the long side you will only have two walls? 

See ביאור הלכה ס’ שס”ג סע’ ל “אינו מניח

https://hebrewbooks.org/pdfpager.aspx?req=60389&st=&pgnum=66