Gemara

(Rava): If something was detached, and later attached, surely it is considered detached regarding idolatry;

If one worships his own house, it is forbidden, even though the Torah forbids only "their gods on the mountains", but not the mountains (or anything else attached).

Tana'im argue about Hechsher (Peros are Mekabel Tum'ah if one of the seven liquids was willingly detached and came on them);

(Mishnah): If a man placed a bowl on a wall so that the bowl will get wet, and water fell on it, the water is Machshir (any Peros that it touches);

If he placed a bowl so the wall will not get wet, water that falls on the bowl is not Machshir.

Question: The Reisha implies that if he wanted the wall to get wet, the water is not Machshir. The Seifa that if he wanted the wall to get wet, the water would be Machshir!

Answer #1 (R. Elazar): We must say that different Tana'im taught the two clauses.

Answer #2 (Rav Papa): The Reisha discusses a wall of a cave. The Seifa discusses a wall that was built (the rocks were once detached, so it is considered detached);

16b Question (Rava): If something was detached and then attached, may it be used for Shechitah?

Answer (Beraisa): If he stuck a knife in the wall and slaughtered, it is Kosher.

Rejection: There he will not leave the knife permanently in the wall. (Rava asked about something attached to be permanent.)

Shevu'os 42b (Beraisa - R. Eliezer): (If Reuven stole Shimon's field and) the river flooded it, he must give to him another field;

Chachamim say, he can say 'your field is in front of you.'

R. Elazar expounds "he will deny his neighbor about a deposit... anything he will swear about" through Ribuy and Mi'ut (inclusions and exclusions). He includes everything (regarding oaths and liability of a Shomer (watchman)), and excludes only documents. Chachamim expound through Klal u'Frat (general and specific terms), and include everything similar to the Prat, i.e. Metaltelim (movable objects) with intrinsic value.

Bava Basra 66a (Mishnah - R. Eliezer): If a baker's board was fixed into the wall, it cannot become Tamei;

Chachamim say, it can become Tamei.

R. Eliezer considers attached Kelim like land, even if they were made and later attached. Chachamim consider attached Kelim to be like Metaltelim, even if they were made after they were attached!

66b: If one intended that rain water wash the frame around a millstone, according to R. Eliezer, anything attached to the ground is like land, so surely the water is not Machshir;

Question (Rav Yosef): According to Chachamim, is the water Machshir? (Is this like intent for something detached?)

This question is not resolved.

Rav Nechemyah brei d'Rav Yosef authorized a girl to collect Parnasah (a tenth of her father's estate, for her dowry), even from a mill frame.

Bava Kama 117b (Rav Papa): R. Elazar holds that land can be stolen. Chachamim disagree.

Sukah 31a (Beraisa - R. Eliezer): A stolen Sukah is Pasul;

Chachamim say, it is Kosher.

Rav Nachman: They argue about one who physically expelled Levi from Levi's Sukah. Chachamim hold that land cannot be stolen, so it is considered borrowed, and one is Yotzei in it.

Rishonim

Rambam (Hilchos To'en 5:5): If Reuven says to Shimon 'you lived in my Chatzer for two months. You owe to me rent', and Shimon says that he lived for only one month, he swears about this, because the claim is not about the house itself, rather, about the rent, which is Metaltelim.

Rambam (Hilchos Mechirah 13:14): Just like Ona'ah (overcharging) does not apply to land, the same applies to rental of land. Even if one rented a great hall for a Dinar for a year, or a small pen for a Dinar for a day, there is no Ona'ah.

Rashbam (Bava Basra 67a DH Agvah): Rav Nechemyah collected Parnasah from Metaltelim that were fixed in the ground. Our Sugya considers them like land, like R. Eliezer. R. Chananel rules like this. This is primary.

Tosfos (Shevu'os 42b DH Shomer): If one borrowed a house and it burned, he is exempt.

Mordechai (Bava Basra 560): Rental of houses is considered like land (regarding collecting a dowry). The Rashbam says so. This is difficult for Sefer ha'Mitzvos, who says that we swear about rental of houses, for it is like Metaltelim.

Tosfos (Bava Basra 66b DH Ba'i): Rabanan hold that a attached board is considered detached regarding Tum'ah. The same applies to Hechsher. This is like the opinion that something detached and later attached to a wall of a building is considered attached. We ask only about a mill frame. It is Batel to the ground regarding a sale. Is it totally Batel, like the wall, and it is considered like land also regarding Hechsher? Or, perhaps it is like attached only in a sale, for people sell generously, but not for Tum'ah, since it is prone to be moved. R. Eliezer considers a board attached regarding Tum'ah, and the same applies to Hechsher. All the more so a mill frame is attached!

Tosfos (16a DH l'Inyan): We do not bring the argument about one who bowed to a tree. Since it is rooted in the ground and came from the ground, it is considered like land.

Poskim

Shulchan Aruch (CM 95:1): Mid'Oraisa, we do not swear about land. We do swear Heses about land.

Rema: Some say that something that was detached and later attached is not like land.

Shach (7): The Tur brings this from Ba'al ha'Itur. He argues with R. Chananel, who rules like R. Eliezer. In Sa'if 5, he discusses attached Peros, and says 'also R. Chananel rules like R. Eliezer.' This is astounding. R. Chananel discussed only Metaltelim that were later attached! Tosfos says that R. Chananel rules like R. Meir, who says that finished Peros are considered like Metaltelim! In Sa'if 7, why did the Tur bring only Ba'al ha'Itur;s opinion? It seems that there is a printing error. R. Chananel should be cited in Sa'if 7 (but not in Sa'if 5). The Tur says 'this is only regarding what grows from the ground, but attached Metaltelim are considered like Metaltelim, for we hold like Chachamim. R. Chananel rules like R. Eliezer.'

Shach (8): The Rema understands that this opinion considers even a house to be detached regarding Shevu'as ha'Shomrim. He learns from the Tur, who said in the name of Ba'al ha'Itur 'we hold like Chachamim regarding a wall of a building, a pipe that was attached, and a beehive.' Darchei Moshe (7) says that the Mordechai (Shevu'os 773) disagrees, and considers a house to be attached. Therefore, if one borrowed a house and it burned down, he is exempt. I say that Ba'al ha'Itur discussed only a wall, but a house is like land. This is why immediately after citing Ba'al ha'Itur, the Tur brought the Rambam in Hilchos To'en, and derived that a house is like land. The Rambam discussed a Chatzer, and the Tur wrote 'house' in place of Chatzer. This shows that it was obvious to the Tur that a house is like land. Even though in Chulin, the Gemara connotes that a house is considered (detached) like a wall, this is regarding Isurim. Regarding money, it is like land. Everywhere we hold that a house is acquired through money, a document or Chazakah, like land. It is called property with Acharayus regarding liens (if a borrower sold it, the lender can collect it from the buyer) and precedence of collection and giving a 10th of one's property for a dowry, and all other monetary laws. The same applies to Shemirah and oaths. The Rambam and Tur say so regarding Ona'ah. Ba'al ha'Itur said that the Halachah follows Chachamim, for they do not discuss a house. Ba'al ha'Itur brought R. Chananel (cited above), who proves from the mill frame that the Halachah follows R. Eliezer, and said 'this is not clear to me.' I.e. R. Chananel is not clear, for Chachamim agree about a mill frame. They argue only about other Metaltelim (that were later attached - PF). The Magid Mishneh (Hilchos To'en 5:5) says that it is clear from Perek 7 of Hilchos Sechirus that rental of land is like land regarding oaths, and there (Halachah 2) the Rambam discusses houses. It is clear that the Mordechai considers houses be attached. Tosfos, Tosfos Yom Tov and Semag say that if one borrowed a house and it burned, he is exempt, for Shemirah does not apply to land.

Magen Avraham (OC 637:7): We can answer all the Shach's questions. Since the land is acquired through money, a document or Chazakah, also the house is acquired through money Agav the land. The same applies to the other (questions).

Machatzis ha'Shekel: He answered the Shach's primary question, that through Shas we say that houses are acquired through money, a document or Chazakah. He did not say how to answer the other questions. We hold that to acquire Agav, one must say 'acquire Agav (or with) the land.' The Gemara never mentions saying 'Agav' to acquire a house. If so, the Magen Avraham's answer does not help for the Rema, who did not decide whether a house is like land. We can say that the opinion that it is like Metaltelim holds that one need not say 'Agav.'

Note: If one sold an Aliyah (upper story), but kept the ground (and ground floor for himself), the Magen Avraham's answer does not apply. Menachos 108b-109a connotes that a document can acquire an Aliyah.

Gra: We hold that something detached and later attached is considered attached regarding Avodah Zarah, Hechsher and Shechitah. Even though Rava was unsure about Shechitah, the Rif, Rambam and Shulchan Aruch do not rule like him. The Rosh holds that if he was Mevatel it (permanently left it there), it is considered detached. This is not the Halachah. Tosfos says that the question was only according to Rabanan. However, we hold like Rav Papa, who distinguishes between the wall of a building and the wall of a cave (the former is considered detached). All the more so, a mill frame is considered detached. This is unlike the Rashbam and R. Chananel. Even though it is considered attached regarding Parnasah and sales, we cannot learn from there to Tum'ah. We hold like Rabanan regarding a board, a pipe to disqualify a Mikveh, and a beehive. We do not learn from attached Peros, for they took root, like Tosfos says.

Rema: Some disagree. Therefore, if one borrowed a house and it burned down, he is exempt. See Siman 301.

SMA (9): Even though a borrower is liable for Ones, here he is exempt.

Gra (11): This opinion learns from "everything attached to the ground is like land.' The Klal u'Frat u'Chlal teaches everything that can be moved, like money and Kelim. Anything attached to the ground cannot be moved.

Shulchan Aruch (OC 637:3): A stolen Sukah is Kosher, e.g. if Shimon expelled Levi from Levi's Sukah and sat in it. This is because land cannot be stolen.

Question (Magen Avraham 7): Why is Shimon Yotzei? The wood is stolen! There is no enactment (to say that the thief acquires, and he merely owes its value), for he did not toil! We must say that what is attached to the ground is like land. This is difficult for the opinion (in CM 95:1) that a house is not considered attached.