Rif Eruvin 24b {Eruvin 76b continues ... 79a}

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24b

{Eruvin 76b continues}
Gemara:
If it {the wall} was not four handbreadths wide, what is the rule?
Rav said: The air of the two domains prevails upon it and {so} no object may be moved even a hairsbreadth.
{Eruvin 77a}
And Rabbi Yochanan ruled: These may bring up {their food} and eat and these may bring up {their food} and eat.

But we learnt {in the Mishna}: "If there was produce at its top – and these may go up from here and eat and these may go up from here and eat..." - going up, yes, but bringing {food} up, no.

This is what it means to say: If it {the wall} has a width of four {handbreadths}, going up, yes, but bringing {food} up, no. But if it does have four {handbreadths} we may even bring up.
And Rabbi Yochanan is consistent with his opinion. For when Rav Dimi came {from Eretz Yisrael}, he cited Rabbi Yochanan: A place which does not have in it 4 x 4 handbreadth is permitted to those in the private domain and to those in the public domain to rearrange their burdens, provided they do not exchange them {with each other from different domains, one placing it down and the other picking it up}.

And this that we learnt {in the Mishna}, "provided that they do not bring down," we establish this, in perek keitzad mishtatfin {Eruvin 87b} for Biblical domains, such as a private domain and a public domain, but Rabbinic domains, such as a wall between two courtyards which is 10 handbreadths high but not 4 handbreadths wide, it is permitted to rearrange one's burden and even to exchange.
And so is the halacha.

{Eruvin 77a resumes}
Rabba bar Rav Huna cited Rav Nachman: A wall between two courtyards [whose one side is] ten handbreadths high and its other side is level with the floor.

courtyard
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XXXXXXXXX courtyard
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it {the wall} is assigned to the courtyard whose floor is level with it, for this {level one} utilizes it {=the wall} easily, while this one utilizes it with difficulty. And in any case when this one utilizes it easily and this one utilizes it with difficulty, we grant it to the one that utilizes it easily.

Rav Shizvi cited Rav Nachman: A trench between two courtyards which was ten handbreadths deep and four handbreadths wide, and one side was level with the ground, we grant it to the one to which it is level with the ground, for this one uses it easily and that one uses it with difficulty, and so we grant it to the one which uses it it easily.

{Eruvin 78b}
Mishna:
If a trench between two courtyards is ten deep and four wide – they make two eruvs and they may not make one eruv, even if it is full of stubble or straw;
{But if} full of earth or gravel – they make one eruv, and they do not make two eruvs.

{The remainder of the Mishna in the gemara is quite different.}
If he put on it a board that is four handbreadths wide, if they want they may make one eruv.
Less than four handbreadths, they make two eruvs and may not make one eruv.

And similarly two balconies, this opposite this {and they placed a board four handbreadths wide} – they make one eruv and may not make two eruvs. {In Mishna in the gemara, the law was the same as for a trench - that they may make either one or two.}
Less than this { < style="font-style: italic;">eruvs and may not make one eruv.

{Eruvin 79a}
Gemara:
Rava said: This {about the board} was taught