#All materials are permissible to be for the walls of a [[Sukkah]] (see next halacha). Some say that that a pious person should preferably only use materials that aren't Biblically unfit for [[S'chach]]. <ref>The Mishna Sukkah 12a declares that all materials are valid for the walls. Shulchan Aruch 630:1 codifies this. Interestingly, the Bach OC 630:1 writes that a pious person should be strict for the Or Zarua (Hilchot Sukkah 2:289:2 quoted by Hagahot Ashri 1:24) who holds that one should not use materials that one may not use for schach for the walls of the sukkah, such as materials that are susceptible to impurity. The Biur Hagra 630:1 questions the Hagahot Ashri, since the Yerushalmi he quotes as a proof, in fact says exactly the opposite. Beiur Halacha s.v. Kol quotes two reasons that a pious person should be strict only to use materials that are not unfit biblically for [[S'chach]] based on the Bach siman 630, but quotes others who reject this stringency. See Chazon Ovadia [[Sukkot]] 1-2 for a list of poskim as well even though he allows the use of these materials. Chazon Ovadia pp. 1-2 as well as Aruch Hashulchan 630:1-2 both say that most achronim do not hold of this stringency and allow one to use materials that are mekabel tumah for the walls. </ref> Nonetheless, one should avoid using any material that emits a foul odor.<ref>Rama 630:1</ref>
#Accordingly, one may even form a sukkah outside of one’s car by opening the doors on one side of the car and placing schach over them.<ref>R’ Moshe Heinemann permits this (http://www.jewishworldreview.com/1000/sukkah.car.html) . When building one’s sukkah in this manner he should also ensure that 1) the doors of the sukkah reach within three tefachim of the ground, to accomplish this it may help to park near the curb (see section titled “Lavud”) 2) the door on the opposite side of the car remains closed, 3) one may not use the seat of the car as one’s table even if he only plans to eat under the schach. </ref>
#Many authorities hold that plastic curtains (tarp, canvas) are unfit for walls of a [[Sukkah]], while others permit. [This is not because of an issue with the material itself but because of an issue with it blowing in the wind.] <ref>Rav Ovadiah Yosef in Chazon Ovadyah (pg 1-5), Yabia Omer OC 9:59, and Yechave Daat 3:46, Rav Menashe Klein Mishnah Halachot 512, Rav Chaim Zonnenfeld in Salmat Chaim 254 and Rav Shlomo Zalman Auerbach in Halichot Shlomo ([[Sukkah]] 7:1 pg 97) hold that plastic curtains that sway in the wind even slightly are unfit for walls of a [[Sukkah]]. [http://www.yutorah.org/lectures/lecture.cfm/764662/Rabbi_Hershel_Schachter/%D7%A2%D7%A0%D7%99%D7%99%D7%A0%D7%99_%D7%99%D7%95%D7%94%D7%9B'%D7%A4_%D7%95%D7%A1%D7%95%D7%9B%D7%95%D7%AA Rav Hershel Schachter] (min 72-80) explains that even though the Chazon Ish (hilchot eruvin 13:6) was lenient, most poskim are strict.
Rav Schachter leaves an absolute guideline unclear but in a situation of extreme need one could rely on the Chazon Ish.<br />
*In Gemara Sukkah 24b, Rav Acha Bar Yaakov states that a wall that cannot stand in the wind is not considered a valid wall. The Chazon Ish (Hilchot Eruvin 13:6) suggests that a wall is not valid only if it falls or sways more than three tefachim in normal wind. However, Rav Ovadia Yosef in Chazon Ovadia pp. 1-5 and Rav Shlomo Zalman Auerbach (Halichot Shlomo Sukkah 7:1 p. 97) hold that plastic curtains that sway in the wind even slightly are unfit for walls of a Sukkah. Rav Ovadia adds, based on Shulchan Aruch 630:10, that this is true even if one ties down the ends because we are concerned that the ties will loosen and that he will not notice. Rav Moshe Feinstein in Sh”t Iggrot Moshe 5:40:2 writes that one should not misinterpret the prevalence of these canvas sukkot as an endorsement of their validity. On the other hand, some achronim (Rav Sonnenfeld, Rav Menashe Klein, and Rav Shternbuch all cited in Piskei Teshuvot 630:9) justify the common practice to use canvas Sukkot since nowadays they are put together well, so the concern of the Shulchan Aruch that the ties may become loose no longer applies.