Eruvin 3 - Partially high enough
We learned that an alley requires a beam at its entrance, in order to separate it from the street and to permit carrying in the alley on Shabbat. The beam should be placed no higher than twenty amot (about 40 feet). The same measurement is true for the sukkah - its covering should not be higher than twenty amot. In both cases the reason is that people should notice and be mindful of it.
What if the beam is partially higher than twenty amot and partially lower? And the same question can be asked about a sukkah. Rabbah said, "It is OK for an alley but not OK for a sukkah." Why? The same reasoning should apply to both! - The answer is that sukkah is a private dwelling, so if its covering gradually thins out and all of it is too high, one who lives in it may not notice. However, an alley is used by many and they will remind each other.
In another version Rabbah said just the opposite. What is the reason in this case? One who lives in the sukkah knows that it is up to him to keep it kosher. However, with an alley everyone relies on someone else to check. As the proverb has it, "When two people cook, the dish is neither hot nor cold."
What is the final conclusion? It is OK in both cases, since the correct understanding of "too high" is "the airspace is too high."
Art: Franz Skarbina - A Back Alley in Hamburg
Don't understand a point? Ask MosesAI about it.