Talmud - Eruvin 78a עירובין ע״ח א׳

If a projection four by four handbreadths in area extends from a wall, and one placed a ladder of any width against it, if the rungs of the ladder are less than three handbreadths apart, he has diminished the height of the wall by means of this ladder and projection.

The Gemara qualifies this statement: And we said this only in a case where one placed the ladder directly against the projection, so that the ladder serves as a passage to it. However, if he placed it adjacent to the projection, he has merely widened the projection, while the ladder remains separate from it. Consequently, the projection does not have any connection to the ground, and a projection that is not within three handbreadths of the ground does not diminish the height of a wall.

And Rav Naḥman said that Rabba bar Avuh said: If a wall between two courtyards is nineteen handbreadths high, it requires one projection to render the use of the wall permitted. If there is a single projection in the middle of the wall, with a ladder of any width resting against it, it is considered a passageway between the courtyards, as the projection is within ten handbreadths of the top of the wall.

However, if the wall is twenty handbreadths high, it requires two projections to render the use of the wall permitted, one within ten handbreadths of the ground, and the other within ten handbreadths of the top of the wall. Rav Ḥisda said: And this applies only where he positioned the projections not directly one above the other, so that it is possible to use a ladder to climb from one projection to the other.

Rav Huna said: If a pillar in the public domain is ten handbreadths high and four handbreadths wide, so that it is considered a private domain, and one drove a stake of any size into the top of it, he has diminished its area. The usable area is now less than four handbreadths, and therefore the pillar is no longer considered a private domain.

Rav Adda bar Ahava said: This applies only if the stake is at least three handbreadths high. If it is less than three handbreadths high, it is considered part of the top of the pillar, based on the principle of lavud. This is in contrast to Abaye and Rava, who both say: Even if the stake is not three handbreadths high, the pillar is no longer considered a private domain.

What is the reason for the opinion of Abaye and Rava? It is that the pillar is no longer fit to be used, as a surface of four by four handbreadths is suitable for use only when it is level. If it has even a small projection, it is no longer usable.

Rav Ashi said: Even a stake three handbreadths high does not diminish the area of the pillar. What is the reason for this? It is that it is possible to hang an item on it. Although it is no longer possible to rest objects on top of the pillar, it is still useful in some way.

Rav Aḥa, son of Rava, said to Rav Ashi: According to your opinion, if he filled it entirely with stakes, i.e., if he drove so many stakes into the top of the post that it was completely filled, what is the halakha?

Rav Ashi said to him: Did you not hear that which Rabbi Yoḥanan said? He said that a pit and its embankment of stone around the edge join together to complete the measure of ten handbreadths. Similarly, the width of the embankment joins with the diameter of the pit to complete the measure of four by four handbreadths necessary to define the pit as a private domain.

There, too, one can raise the question: But why? He cannot use the embankment, as most of the area is the empty space of the pit. Rather, what have you to say, i.e., how can you solve this problem? The solution is that he places an item, e.g., a board, over the mouth of the pit, and then he can make use of it. Here, too, he places an item over the stakes and can make use of the pillar.

Rav Yehuda said that Shmuel said: If a wall is ten handbreadths high, it requires a ladder fourteen handbreadths high, so that one can place the ladder at a diagonal against the wall. The ladder then functions as a passageway and thereby renders the use of the wall permitted. Rav Yosef said: Even a ladder with a height of thirteen handbreadths and a bit is enough, as it is sufficient if the ladder reaches within one handbreadth of the top of the wall.

Abaye said: Even a ladder that is only eleven handbreadths and a bit suffices, as the ladder will still reach a height of over seven handbreadths, i.e., within three handbreadths of the top of the wall.

Rav Huna, son of Rav Yehoshua, said: Even if the ladder is only seven handbreadths and a bit it is sufficient, as he can stand the ladder upright against the wall. Since it will reach within three handbreadths of the top of the wall, the principle of lavud applies. Therefore, even a ladder placed in this manner is considered a valid passageway between the two courtyards.

Similarly, Rav said: An upright ladder effectively diminishes the height of a wall, as it creates a passageway. I received this teaching as a tradition, but I do not know what the reason is, as people do not generally climb ladders positioned in this manner.

Shmuel said: Does Abba, i.e., Rav, actually not know the reason for this matter? The reason here is just as it is in the case of a platform above another platform. Even though it is not easy to climb, since it provides steps that can be climbed, albeit with difficulty, it is considered a valid passageway.

Rabba said that Rabbi Ḥiyya said: The trunks of palm trees in Babylonia that were placed next to a wall between two courtyards so that people could climb on them and pass from one courtyard to another do not need to be established permanently and attached to the ground; rather, they serve to diminish the wall as they are. What is the reason for this? It is that their heaviness establishes them as connected to the ground. Although it is permitted to handle them, nevertheless, since their weight makes them difficult to move, they are considered fixed in place.

And similarly, Rav Yosef said that Rabbi Oshaya said: Ladders in Babylonia do not need to be established and fixed permanently in place. What is the reason for this? It is that their heaviness establishes them, as the ladders in Babylonia were typically large and heavy.

The Gemara comments: With regard to the one who said that Babylonian ladders do not need to be fixed in place, all the more so would he agree that the trunks of palm trees, which are placed there from the outset for this purpose, are considered fixed, as both are extremely heavy and also designed to remain in place. On the other hand, the one who said that the trunks of palm trees need not be fixed permanently in the ground, spoke only with regard to palm trees. However, as for ladders, no, they are not considered fixed in place. A ladder, even a heavy one, is designed to be moved from place to place.

Rav Yosef raised a dilemma before Rabba: If there is a narrow ladder measuring less than two handbreadths wide on one side, and a similarly narrow ladder on the other side, and there are rungs of woven straw in the middle between them which would not support a person’s weight, what is the halakha? Are the two ladders considered a single unit, forming a ladder four handbreadths wide, which serves to diminish the height of a wall?

Rabba said to him: The sole of the foot cannot climb upon them. A person usually places his foot in the middle of a ladder. Since the middle of this ladder is made of straw, then although it appears to be four handbreadths wide, it is not fit for use and does not diminish the height of the wall.

Rav Yosef continued to ask: And what if there were rungs of straw on one side and rungs of straw on the other side, and a narrow ladder less than four handbreadths wide in the middle, and their combined width is four handbreadths? What is the halakha in this case? Rabba said to him: The sole of the foot can climb upon them, and the ladder appears to be four handbreadths wide. Therefore, it serves to diminish the height of the wall.

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

Eruvin 78a examines how ladders and wall projections affect shared courtyard boundaries, plus how a stake diminishes a pillar's private domain status.