1) HALACHAH: AN UMBRELLA ON SHABBOS
QUESTIONS: The Gemara says that a person is permitted to unfold a folding chair ("Kisei Traskal") on Shabbos even though he thereby creates a shelter over the space underneath the chair.
(a) What is the Halachah with regard to opening an umbrella on Shabbos? Is it the same as a folding chair?
(b) Furthermore, if an umbrella is opened before Shabbos, may one carry it over his head on Shabbos? Is it the same as standing a bed upright that was on its side, which the Gemara permits?
(a) The NODA B'YEHUDAH (OC 1:30) says that one is not permitted to open an umbrella on Shabbos, because one thereby creates an Ohel. The CHASAM SOFER (OC 72) also prohibits opening an umbrella. (See CHAZON ISH, OC 52:6.)
The BI'UR HALACHAH (OC 315:7) explains that an umbrella is not similar to a folding chair, because such a chair unfolds right into position. An umbrella, however, is different, because the metal rods keep the umbrella locked in the open position, and these must be clicked into place when unfolding the umbrella. Because of this, opening an umbrella is deemed constructing an Ohel, and not merely putting an object in a different position.
(b) Regarding an umbrella that was opened prior to Shabbos, the Bi'ur Halachah writes that one is prohibited to carry it on Shabbos because wherever a person walks while he carries the umbrella, he makes a new Ohel in that place (since he is holding the umbrella for the sake of using it as an Ohel, which protects the space underneath it).
Of course, in a place where there is no Eruv, one is prohibited to carry an umbrella because doing so constitutes Hotza'ah in Reshus ha'Rabim.
2) HALACHAH: WEARING A WIDE-BRIMMED HAT ON SHABBOS
OPINIONS: The Gemara discusses the conditions under which one may wear a "Siyana" on Shabbos. What is a Siyana, and under what conditions may one wear it on Shabbos?
(a) RASHI explains that a Siyana is a wide-brimmed hat. If it is not worn tightly (Mehudak) on the head, there is a concern that the wind might blow it off and one will pick it up and carry it in Reshus ha'Rabim. (According to Rashi, "Mehudak" means "tight" and is the condition that permits a wide-brimmed hat to be worn on Shabbos.)
(b) TOSFOS cites RABEINU CHANANEL who says that a Siyana is a hat or head covering. If the brim is made from a hard material that does not bend, the hat may not be worn on Shabbos, because it is considered an Ohel. When the brim is soft and pliable, the hat may be worn on Shabbos. (According to Rabeinu Chananel, "Mehudak" means that it "does not bend" and is the condition that prohibits a hat to be worn on Shabbos.)
(c) The RAMBAM writes that a Siyana refers to any Talis or overgarment which a person drapes over his head and which protrudes in front of him or to the sides. If it is tightly bound to his head and it is stiff and does not bend, it is like an Ohel and may not be worn. (Apparently, according to the Rambam, "Mehudak" means both that it is "tight" and that it "does not bend," and it is the condition that prohibits a hat to be worn. See TESHUVOS RADVAZ in Leshonos ha'Rambam.)
HALACHAH: Is one permitted to go outside with a hat with a wide, stiff brim on Shabbos? According to Rabeinu Chananel, to wear such a hat should be prohibited, because it is like an Ohel. According to Rashi, it should be prohibited only if it is not worn tightly on one's head.
The MISHNAH BERURAH (OC 301:152) lists a number of reasons to permit one to wear a hat on Shabbos:
First, the MAGEN AVRAHAM rules that if the brim of a hat is sloped downward, it is not considered an Ohel and may be worn.
Second, one may rely on Rashi's opinion that it is prohibited only when it is worn loosely.
Third, the hats commonly worn today are not worn in order to provide shade, and thus they do not serve the purpose of an Ohel.
Finally, if the brim is not stiff, the hat certainly is permitted.
3) SETTING UP A "GUD B'KISNA" ON SHABBOS
OPINIONS: Rav says that a "Gud b'Kisna" may be spread by two people on Shabbos but not by one person. Abaye adds that a "Kilah" may not be spread even by ten people. What are these objects and why are they forbidden to be spread?
(a) RASHI cites the explanation of his teachers who say that a "Gud b'Kisna" refers to a removable leather pouch (used for storing liquids) that is attached by its straps to its normal resting place. Two people may set it up on its normal resting place because they are unable to stretch it properly. One person, though, is able to set it up properly by stretching one side around one peg and tying it, and then stretching the other side around the other peg and tying it. Rashi concludes that he does not know what this is (that is, why two cannot tie it tightly, or why it is prohibited if it is done tightly).
(b) The RA'AVAD (Hilchos Shabbos 22:32) explains that "Gud b'Kisna" refers to a horizontal curtain hung from rings that protrude from the walls on either side. If the curtain can be hung without stretching out the creases, it is permitted, because it does not appear that an Ohel is being made, or that the creases are being stretched out and the curtain "fixed." (Apparently, the Gemara refers to a curtain that was already spread one Tefach before Shabbos, and thus it may be spread the rest of its length on Shabbos.) If the creases are stretched, however, it appears as though a new Ohel is being made (since the change in creases makes it appear like a new fabric) or as though the curtain is being fixed.
One person may not set up the curtain because he is unable to line up the rings properly and he has no choice but to stretch out the creases. Similarly, when ten people put up a large curtain (a "Kilah"), they are unable to line up the rings properly and they will have to change the creases.
(c) The RAMBAM (Hilchos Shabbos 22:32) says that a "Gud b'Kisna" is a hanging curtain. It may not be hung by one person, because it is not possible for him to hang it without it draping over and forming a roof (Ohel) at some point. Two people, though, are able to hang it without it draping over and forming a roof. However, a canopy with a horizontal roof built into it may not be set up vertically to be used as a divider even by ten people, because it is inevitable that at some point its roof will lift up slightly and form an Ohel over the ground.
(d) The RASHBA in the name of RABEINU YONAH also says that Gud b'Kisna is a curtain. If this curtain is set up all at once (by two people), it is not similar to Binyan (which is done in progressive stages) and it is permitted. However, if one part is placed into position first and then the next part, it looks like an act of Binyan and is prohibited.
Since one person can set up a "Gud" only part by part, it is prohibited. A large curtain cannot be set up all at once even by ten people, and therefore it is prohibited.