Gemara

Question (Levi bar Shmuel): May one assemble a bed of Tarsim (traveling craftsmen. The bed comes apart.)

Answer (R. Aba and Rav Huna bar Chiya): It is permitted.

Rav Yehudah: Rav and Shmuel say that one who assembles such a bed is liable!

Question (against R. Aba and Rav Huna - Beraisa): One who assembles a Menorah of rings [that come apart] is liable;

One may not assemble a plasterer's rod. If he did so, he is exempt.

R. Simai says, one who inserts [a flute] in a round horn [a musical instrument with holes] is liable [for it must be wedged in tightly]. One who inserts it in a straight horn is exempt. (It goes in loosely.)

Answer: R. Aba and Rav Huna hold like R. Shimon ben Gamliel:

(Beraisa): One may not return Malbenos (coverings for legs) of beds, legs of beds, or the wood on a bow (on which the arrow rests). If he did so, he is exempt;

He may not be Toke'a (wedge) them in tightly. If he did, he brings a Chatas;

R. Shimon ben Gamliel says, if they fit loosely, it is permitted.

There was a Gelalnisa bed (like of Tarsim) in Rav Chama's house. He would assemble it on Yom Tov.

Question (a Chacham, to Rava): Do you [not rebuke him because you] hold that [it is not wedged in tightly, so] this is like building non-professionally? Granted, it is permitted mid'Oraisa, but it is forbidden mid'Rabanan!

Answer (Rava): I hold like R. Shimon ben Gamliel, who permits if it fits loosely.

122b (Beraisa): One may take the door of a chest, box or cupboard, but he may not return it.

(Rava): The Tana holds that Binyan and Stirah do not apply to Kelim. He decrees to forbid returning, lest one be Toke'a it.

Rishonim

Rif and Rosh (21b and 3:23): the Halachah follows R. Shimon ben Gamliel.

Ran (DH v'Ika): Some say that since we conclude like this, this shows that Binyan does not apply to Kelim. If Binyan applied, even without Teki'ah one would be Chayav Chatas for tightening. We would decree about what is [normally] loose due to what is tight. Rather, Binyan does not apply to Kelim. Even tightening is forbidden only mid'Rabanan. This is a decree lest one be Toke'a, which is liable for Makeh b'Patish. Therefore, we permit what is [normally] loose.

Hagahos Ashri: Based on the beginning of Perek 4, we must say that we permit only something that is not normally Teku'ah, if it is loose (Mahari'ach).

Rambam (Hilchos Shabbos 22:26): One may not return a Menorah of rings, or a chair or table that comes apart, or similar things, for this looks like building. If he returned it, he is exempt, for Binyan and Stirah do not apply to Kelim. If it was loose, one may return it.

Rambam (26:11): One may not move a big or small Menorah of rings, lest he reassemble it.

Magid Mishneh: The Rashba forbids even if it is semi-loose. If it is totally loose, it is permitted.

Hagahos Ashri (4:5): If Tzaltzelim (clappers?) came off a smock, one may return them, since they were already on it, as long as he does not do so in a way that there is concern lest he be Toke'a them. If they are normally tied and Teku'ah, it is forbidden, just like we forbid returning the door of a chest, lest one be Toke'a it.

Poskim

Shulchan Aruch (OC 316:6): One may not return a bed of rings and tighten it. If he was Toke'a it, he is Chayav Chatas.

Taz (6): This is the final Melachah. One is liable for Makeh b'Patish.

Magen Avraham (10): If he was Toke'a, he is Chayav Chatas, for he made a Kli.

Kaf ha'Chayim (64): This is if it will stay assembled.

Mishnah Berurah (40): The beds are for craftsmen, who carry them on the road, and when they reach their [lodging] place, they assemble them.

Mishnah Berurah (41): If he is Toke'a it in with pegs and nails, this is the final Melachah. He is liable for Makeh b'Patish. Some say that since he makes a full Kli, he is liable for Boneh. See 314:1 and the Gra there.

Kaf ha'Chayim (61): The Levush connotes that tightening is a Melachah. Tosefes Shabbos challenged this, for this is unlike the Ran.

Kaf ha'Chayim (63): The same applies to a crib that disassembles. The middle beam normally fits tightly in the side walls. Therefore, if it came apart, one may not return it on Shabbos.

Shulchan Aruch (ibid.): If it is (Rema - normally) loose, one may return it l'Chatchilah (Rema - as long as he does not make it tight).

Magen Avraham (11): Semag says that we forbid only something that requires strength and skill.

Kaf ha'Chayim (62): The Shulchan Aruch forbids to return it or tighten it. One could have erred to say that he forbids only to return and tighten it. Therefore, the Rema added that when it is normally loose, one may return it without tightening it. This shows that in the Reisha, when it is normally tight, even returning it alone is forbidden.)

Beis Yosef (DH Mitah): The Rif, Rambam and Rosh rule like R. Shimon ben Gamliel. It seems that the Rambam explains 'if it was loose' to mean 'if it was normally loose.' Therefore, one may return it. However, if it is normally tight, it is forbidden, even if now he returns it loosely. Also the Tur connotes like this regarding a cup of Perakim. (It can be disassembled.) He permits returning it, for it is not normal to make it tight. This connotes that if it were normally made tight, it would be forbidden, even if now he leaves it loose. It seems that Hagahos Ashri agrees. Also the Kolbo writes in the name of the Ra'avad 'things that one is not particular if they move in the hole, one may insert them in the hole. We decree lest one be Toke'a only regarding something that must be held tightly.'

Kaf ha'Chayim (65): The Shulchan Aruch and Acharonim hold like the Ra'avad, who permits what is normally loose in the hole. However, we forbid what is attached to the ground, e.g. a door, even if it is loose, for this is Binyan.

Shulchan Aruch (ibid.): One may disassemble and return a cup of Perakim on Shabbos.

Mishnah Berurah (44): This is a cup that one removes from its base.

Beis Yosef (DH v'Ra'isi): The Tur brings in the name of Maharam that a cup of Perakim is similarly [forbidden]. However, R. Yerucham, in the name of R. Peretz, permits, like the Tur.

Taz (7): Seemingly, tin flasks with screws, one may not make them tight, just like a bed of Perakim. The latter opinion holds that we should have forbidden even tightening it loosely, since it is normal to tighten it. However, it seems that they are stringent only for a cup, for one need not disassemble it. Its primary use is not through disassembling it. The flask is different. It is used mainly through constant disassembling. Even if he would be Toke'a it forcefully, this is not final Melachah. Surely, one must be careful not to disassemble a cup at all, like Maharam, since it is not needed for Shabbos. If there is a big need, one may be lenient.

Magen Avraham (12): Our cups have grooves and fit tightly. All forbid them. This is unlike covers of Kelim that are made that way. They are not made to be permanent[ly closed]. Rather, one constantly opens and closes them. The Poskim connote that one may move these Kelim. We decree only about a Menorah, which it is normal to disassemble (269:1). The same applies to everything similar. One may move something that it is not normal to disassemble.

Kaf ha'Chayim (70): Kelim that are made to constantly open and close them, one may even be Toke'a them.

Mishnah Berurah (45): Since it is not normal to tighten it so much that it would be considered Toke'a, we are not concerned for this. The other opinion holds that since in any case it is normal to tighten, it is forbidden even if it is loose, just like a bed of Perakim.

Shulchan Aruch (ibid.): Some say that a cup is like a bed.

Magen Avraham (13): The same applies to a Stender in a Beis ha'Keneses on which we rest Seforim.

Rema: If it is normally tight, even if now it is loose, it is forbidden.