Sukkah 4B

פחות משלשה טפחים ⁠— כשרה.

If the distance from the edge of the dug-out area to the wall was less than 3 handbreadths then it is fit, as the edge of the dug-out area is joined to the wall of the sukka based on the principle of lavud.

מאי שנא התם, דאמרת פחות מארבע אמות, ומאי שנא הכא, דאמרת פחות משלשה טפחים?

The Talmud asks: What is different there, in the case of a sukka with a platform in its center, that you said that it is a fit sukka if the wall is at a distance of less than 4 cubits from the edge of the platform, and what is different here that you said the wall must be at a distance of less than 3 handbreadths for the sukka to be fit?

התם, דאיתיה לדופן, פחות מארבע אמות ⁠— סגיא, הכא, לשוויי לדופן, פחות משלשה טפחים ⁠— אין, אי לא ⁠— לא.

The Talmud answers: There, in the case of the sukka more than 20 cubits high, where there already is a wall, but it is removed from the platform, as long as the wall is at a distance of less than 4 cubits, it is sufficient to render the sukka fit. Here, where the sukka is less than 10 handbreadths high, its wall is not a fit wall. In order to render it a wall by adding the height of the dug-out area, if the distance between them is less than 3 handbreadths, yes, the dug-out area is considered joined to the wall, as based on the principle of lavud two objects are considered joined if the gap between them is less than 3 handbreadths; and if not, no, they are not considered joined.

היתה גבוהה מעשרים אמה, ובנה בה עמוד שהוא גבוה עשרה טפחים, ויש בו הכשר סוכה ⁠— סבר אביי למימר, גוד אסיק מחיצתא.

If a sukka was more than 20 cubits high, and one built a pillar in the sukka, far from the walls, that is 10 handbreadths high, and the distance from the top of the column to the roofing was less than 20 cubits, and on the horizontal surface of the column there is a bit more than 7 by 7 handbreadths, the minimum area required for fitness of a sukka, Abaye thought to say that this is a fit sukka because of the principle: Extend and raise the partitions of this pillar. Given that the column is at least 10 handbreadths high, its 4 sides are therefore considered partitions, and the halakha is that the legal status of a partition is as if it extends and continues upwards indefinitely. Based on that perspective, the surface of the column is supported by 4 partitions at least 10 handbreadths high that extend upward indefinitely, and from the top of the pillar to the roof is less than 20 cubits; therefore, this squared column forms a fit sukka.