Apropos forming a sukka wall based on the principle of lavud, the Gemara cites that Rabbi Ami said: A board that measures four handbreadths and a bit can permit the use of a sukka, serving as a wall, and it is effective if one establishes it less than three handbreadths from the adjacent wall. And the principle states: The legal status of any objects with a gap of less than three handbreadths between them is as if they were joined.
...
The Laws of the Walls of the Sukkah, 13 Seifim:
All materials are valid for the walls of the sukkah (and it is not necessary to erect things similar to how they grow) (Tur). Even if the sukkah's sunlit area is greater than its shaded area due to the walls, it is still valid. Rema: In any case, one should not make the sides of the sukkah out of something that smells bad [R"an] or something that will wither within seven days such that it will not have the minimum measurements of a wall (his own opinion).
Regarding the walls of the sukkah, if there are two walls adjacent to each other like a gamma, one makes a wall that has its width greater than a tefach and puts it within three [tefachim] from one wall. One then places a rod (parallel to the wall) (Tur) over this tefach[-wide pseudo-wall] to make the form of a doorway, placing a rod on top of [the real wall] and on top of the tefach[-wide pseudo-wall], and it is kosher, even if the rod does not touch them. Rema: And if the tefach [pseudo-wall] and the wall reach schach, no rod is needed above them (Mordechai, Hagahot Maimoni ch. 4). And the custom that the form of the doorway is circular is just for decorative reasons (so wrote Mordechai).
Mg"Á és MB szerint csak akkor jó, ha megvan a négy fal.
...
...
Áh"S mékél: 3 fal elég, PT hoz más véleményeket is, Rási nevében is.
...
Szélfútta falak: le kell őket kötözni.
If one makes his sukkah between trees with the trees as its walls, if they are strong or tied and secured such that normal wind will not regularly shake them, and the open spaces are filled in with straw and hay such that the wind will not shake them, and they are tied, it is kosher. Therefore, it is not good to make the walls from sheets of flax without poles even if they are tied well because sometimes they unintentionally get detached and you have a wall that cannot withstand a normal wind. If one wants to use sheets, it is good to weave poles into the walls every three [tefachim].