Gemara

(Mishnah - R. Eliezer): If a window stopper is tied and hangs [above the ground], one may use it to close a window. If not, one may not;

Chachamim permit in either case.

(Rabah bar bar Chanah): All forbid making a new temporary Ohel even on Yom Tov [and surely on Shabbos].

R. Eliezer forbids adding even on Yom Tov;

Chachamim permit adding even on Shabbos.

138a (Abaye): The following are forbidden, but if one did them he is exempt -- stretching out a leather pouch on pegs (this is like making an Ohel), hanging a Meshameres (a cloth spread over a Kli for straining wine), and spreading a Kilah (a canopy over a bed);

If one made a permanent Ohel, he is Chayav Chatas;

The following are permitted -- putting a bed (that was on its side) on its legs, and opening a folding chair or toilet seat.

(Rami bar Yechezkeil - Beraisa): One may not spread a folded Talis. If he did, he is exempt.

If it was wrapped on a pole by a thread or string from before Shabbos, one may spread it on Shabbos.

Also Rav told Rav Kahana that it is permitted only in the latter case.

Rav Yosef: I saw the Kilos of Rav Huna's house. On Shabbos night they were spread, and on Shabbos morning they were [dismantled] on the floor.

(Rav citing R. Chiya): One may spread a curtain [in a doorway] and take it down.

(Shmuel citing R. Chiya): One may spread Kilas Chasanim (a canopy spread over a pole running lengthwise above the middle of the bed. It slopes down on both sides) and take it down.

(Rav Sheshes brei d'Rav Idi): This is only if the top is not a Tefach wide, and within three Tefachim of the top, the width [between sides] is not a Tefach, and [at the bottom] the sides are not a Tefach from the middle, and it does not hang a Tefach below [the sides of] the bed.

Rishonim

Rif (56b): Rami bar Yechezkeil taught about a folded Talis tied between two walls. It reaches down to the floor. One sleeps under it, for shade. The roof is less than a Tefach, therefore it is only Ohel Arai. If there was a string on it from before Shabbos, it would be permitted to stretch it out now.

Question (Rosh 20:2): The Rif brought the Heter to spread and take down Kilas Chasanim when the top is not a Tefach wide, and it is not a Tefach wide within three of the top. Why is this different than a folded Talis, which is Binyan Arai more than Kilas Chasanim? Rather, the Talis' roof is a Tefach. Alternatively, after the slope ends, it hangs down straight a Tefach, like it says about Kilas Chasanim. It is permitted when there is a string on it is even if it was not spread out a Tefach, rather, it was wound. Being wound on a string is as if it was spread out a Tefach. The Kilos of Rav Huna, Rav Papa and Rav Huna brei d'Rav Yehoshua were spread at night, and in the morning they were on the floor. This was through a string, or they are Kilos Chasanim.

Poskim

Shulchan Aruch (OC 315:1): One may not make an Ohel on Shabbos or Yom Tov, even an Ohel Arai. This refers to a roof. One may make Mechitzos. A Mechitzah is forbidden only if it is in order to permit a Sukah or carrying.

Beis Yosef (DH Asur): Rashi (125b) explains that one may not make an Ohel Arai on Shabbos, i.e. to spread a mat on four poles for shade. Only a roof is forbidden. A Mechitzah is not an Ohel. One may not put a window stopper because it [the house] is a Binyan Keva, so it looks like adding to Binyan.

Magen Avraham (1): The Beis Yosef says that since it moves back and forth in a normal wind, and it does not stop people from passing through, it is called not Kavu'a. One may not add to an Ohel Kavu'a, like the Ran says (56b DH u'Mitah). See what I wrote in 313:7 [that if a window stopper is removed very rarely, it is an Ohel Kavu'a, and forbidden. This is from the Rosh Eruvin 10:15].

Mishnah Berurah (1): One who makes an Ohel Kavu'a, e.g. he spreads a mat or sheets for an Ohel that will last, even if it is not proper Binyan, he is liable for Boneh. Making an Ohel is a Toladah of Boneh. One who destroys it is liable for Soser. Chachamim decreed about an Ohel Arai due to an Ohel Kavu'a, and about Stirah of an Ohel Arai due to Stiras Ohel Kavu'a.

Mishnah Berurah (2): A roof is forbidden even without Mechitzos underneath, e.g. to temporarily spread a sheet on four poles to protect from sun or rain.

Mishnah Berurah (3): The primary part of an Ohel is the roof. Therefore, Chachamim decreed about it due to an Ohel Kavu'a. Mere Mechitzos are not considered an Ohel at all!

Kaf ha'Chayim (1): Rashi explains that Ohel Arai is one that is temporary. If one puts a sheet on four poles and ties it, or even without tying, if he intends for a long time, he is Chayav Chatas for an Ohel Kavu'a, if it is a Tefach by a Tefach. One is Chayav Chatas even for adding to an Ohel Kavu'a. Perhaps one is liable even for a fixed Mechitzah on the side a Tefach by a Tefach.

Kaf ha'Chayim (11): If one's Sukah fell on Yom Tov, he may not tell a Nochri to put Schach on it. Since it is made for eight or nine days, it is Ohel Kavu'a. The Torah forbids this. For a Mitzvah, we permit telling a Nochri to do only Shevus.

Kaf ha'Chayim (3): One may not open an umbrella on Shabbos, but one may tell a Nochri to hold it to shield the Yisrael (Birkei Yosef). However, Giv'as Pinchas says that if it was open from before Yom Tov, surely one may carry it. We decree on Shabbos, on which one may not carry. The Noda bi'Yehudah (2 OC 30) wavered about an umbrella open from before Shabbos. He concluded to forbid due to Mar'is ha'Ayin, for others do not know that it was open from before Shabbos. Also Ma'amar Mordechai and Pesach ha'Dvir forbid. Since it is forbidden due to Ohel and Mar'is ha'Ayin, Yom Tov is like Shabbos. This is the custom.

Rema: A Mechitzah made for mere privacy is permitted. Therefore one may spread a curtain in front of a doorway, even if it is fixed there,

Gra (DH Af): The Rema rules unlike Rashi in Eruvin (102a DH Mutar, who forbids if it is fixed), rather, like Rashi in Shabbos (138a DH Mutar).

Mishnah Berurah (6): If one ties it on top, on bottom and on the sides so it does not move back and forth in the wind, this is forbidden due to Boneh. This is a fixed Stimah (sealing).

Rema (ibid.): One may spread a Paroches in front of the Aron Kodesh, as long as he does not make an Ohel with a roof that is a Tefach.

Magen Avraham (2): Surely a Paroches is permitted, for the Aron already has a door. The Paroches is merely for Tzeni'us (modesty). Surely one may spread an illustrated sheet for decoration, even though it is fixed there, since it is not a Mechitzah there.

Machatzis ha'Shekel: I.e. even though it is tied above and below and on the sides, so it does not move in the wind, it is permitted because it is not for the sake of a Mechitzah, for there are already walls of the house. It is like a Paroches.

Gra (DH v'Chen): See Sa'if 12 [in which the Shulchan Aruch says that one must be careful not to make an Ohel while spreading it. If it is big, two people must spread it.]

Rema (ibid.): Similarly, one may make a Mechitzah in front of the sun, cold, or in front of the Neros so the wind will not extinguish them. One may not make a Mechitzah in front of the Neros to permit relations, unless it was spread a Tefach before Shabbos. Then, one may increase it on Shabbos.

Mishnah Berurah (11): If a folding Mechitzah was not spread out a Tefach before Shabbos, even if it is more than a Tefach thick, one may open it on Shabbos, for this (its thickness) was not made for a Mechitzah.