Gemara

A Mitzri ladder (it has less than four rungs) is not Mema'et (stop a wall from preventing two Chatzeros from being Me'arev together).

(Rav Ashi): Rav Acha bar Ada taught that it is not Mema'et because it may be moved, and anything that may be moved on Shabbos is not Mema'et.

78a (Rabah citing R. Chiya): [Detached] date trees in Bavel need not be fixed [in the ground. They are Mema'et in any case.]

This is because their weight fixes them. (They are not normally moved.)

He did not teach this regarding ladders. He would say that ladders must be fixed.

Beitzah 9a (Mishnah - Beis Shamai): We may not take a ladder from dovecote to dovecote, but one may tilt it from window to window;

Beis Hillel permit.

Version #1 (R. Chanan bar Ami): They argue about in Reshus ha'Rabim. Beis Shamai hold that an onlooker [who sees him move it] thinks that he needs to plaster his roof, and Beis Hillel hold that the dovecote proves [that he intends for birds]. All permit in Reshus ha'Yachid.

Question: Rav taught that whenever Chachamim forbade due to Mar'is ha'Ayin, it is forbidden even in an inner room [where no one will see him]!

Answer: Tana'im argue about this. R. Chanan holds like the Tana who permits in private.

Version #2 (R. Chanan): They argue about in Reshus ha'Yachid. Beis Shamai hold like Rav, and Beis Hillel disagree. All forbid in Reshus ha'Rabim.

Question: If so, [R. Chanan must say that] Rav holds like Beis Shamai!

Answer: Tana'im argue about this:

(Beraisa): [If one's clothes became wet in the rain,] one may spread them to dry in the sun, but not in public view;

R. Eliezer and R. Shimon forbid [even in private].

9b: Our Mishnah is unlike the following Tana:

(Beraisa - R. Shimon ben Elazar): Beis Shamai and Beis Hillel both permit moving a ladder from dovecote to dovecote. They argue about returning. Beis Shamai forbid, and Beis Hillel permit;

R. Yehudah says, this refers to a dovecote ladder. All forbid an Aliyah ladder (used to go to the second story).

Once, Bnei R. Chiya permitted a ladder.

R. Chiya: Retract and forbid it!

His sons held that since R. Yehudah says that they do not argue about an Aliyah ladder, the first Tana holds that they argue [and Beis Hillel permit].

This is wrong. R. Yehudah explains the first Tana;

We derive this from "we take a ladder from dovecote to dovecote." If this referred to an Aliyah ladder, it should have said "we bring a ladder to a dovecote"! Rather, Beis Hillel permit only a dovecote ladder, but not an Aliyah ladder.

His sons disagree, for it does not say "a dovecote ladder." "From dovecote to dovecote" teaches that one may take it to many dovecotes.

Rishonim

Rif (Beitzah 5a): R. Yehudah says that they argue about a dovecote ladder. All forbid an Aliyah ladder.

Ran (DH mi'Chalon): The Rif did not bring the Sugya because he ruled in Shabbos (62a) like Rav. Therefore, Beis Hillel must totally permit. If they would forbid in Reshus ha'Rabim, they would forbid even in Reshus ha'Yachid!

Ran (5a DH Aval): It is clear from the Gemara that we forbid even tilting an Aliyah ladder from window to window.

Rambam (Hilchos Yom Tov 5:4): One may not take a ladder from dovecote to dovecote in Reshus ha'Rabim, lest people say that he needs to fix his roof, but it is permitted in Reshus ha'Yachid. Even though whenever Chachamim forbade due to Mar'is ha'Ayin, it is forbidden even in an inner room, here they permitted for Simchas Yom Tov.

Rebuttal (Ra'avad): The Rambam says so, but the Gemara did not permit due to Simchas Yom Tov. Rather, Tana'im argue about Rav's law. Rav Chanan holds like the first Tana, and distinguishes between Reshus ha'Yachid and Reshus ha'Rabim. Rav holds like R. Eliezer and R. Shimon, who do not distinguish. Beis Hillel permit both of these. The Rif rules like Rav Yehudah. Therefore, both of them are permitted.

Magid Mishneh: The Rambam discusses a dovecote ladder, since one may not even tilt an Aliyah ladder from window to window. This is clear from the Gemara. The Rambam did not need to explain this, since he already wrote in Hilchos Shabbos (26:7) that one may not move an Aliyah ladder, and he wrote above (1:17) that whatever is forbidden on Shabbos is forbidden on Yom Tov, except for what he explicitly permits.

Rosh (Beitzah 1:14): According to one version, also Beis Hillel forbid in Reshus ha'Rabim. According to the other version, Beis Hillel permit even in Reshus ha'Rabim. The Ge'onim rule leniently for mid'Rabanan laws. The Rif brought the Mishnah simply, for he holds that Beis Hillel permit in every case. R. Yehudah explains the first Tana. The Halachah follows him. One may not move an Aliyah ladder. This is difficult, for in Eruvin we say that a Mitzri ladder is not Mema'et because one may move it on Shabbos!

Suggestion: The Sugya in Eruvin is like the version that says that all permit in private.

Rejection: Even that version permits only a dovecote ladder. Or, perhaps since Beis Shamai forbid a dovecote ladder in Reshus ha'Rabim and permit in Reshus ha'Yachid, all permit an Aliyah ladder in Reshus ha'Yachid. However, R. Chiya forbids here, and in Eruvin he permits! (Therefore, a ladder must be fixed in order to be Mema'et.) R. Tam answered that there he discusses house ladders that are normally moved from corner to corner. They are unlike Aliyah ladders, which are big, and suitable for plastering the roof. R. Avraham of Borgail answered that on Yom Tov, when one may take a ladder to Reshus ha'Rabim, onlookers will say that he needs to plaster his roof. Since we forbid in Reshus ha'Rabim, it is forbidden even in an inner room. On Shabbos, it is not normal to take it to Reshus ha'Rabim, therefore it is permitted in the house. According to this, we may not move our ladders on Yom Tov.

Poskim

Shulchan Aruch (OC 518:4): One may move a dovecote ladder from dovecote to dovecote, even in Reshus ha'Rabim.

Magen Avraham (7): The dovecote ladder proves [that it is not in order to fix the roof]. Other house ladders are forbidden. The Yam Shel Shlomo forbids even in the house. One who is lenient does not lose.

Gra (DH Afilu): Be'er ha'Golah says that for mid'Rabanan laws the Halachah follows the lenient opinion. The Ran says that we do not hold like the Sugya there, rather, like R. Eliezer and R. Shimon, who do not distinguish Reshus ha'Yachid from Reshus ha'Rabim.

Kaf ha'Chayim (36): All forbid returning it to his house. If he fears lest it be stolen, we can say that Chachamim permitted, lest he not take it out [and refrain from Simchas Yom Tov].

Mishnah Berurah (25): One may move it to get birds for Yom Tov, even if it was possible from Erev Yom Tov.

Mishnah Berurah (26): Likewise, if it is standing elsewhere, one may erect it near a dovecote.

Mishnah Berurah (27): The dovecotes were in Reshus ha'Rabim, or he takes the ladder through Reshus ha'Rabim. We are not concerned lest people say that he takes it for Melachah. Dovecote ladders are recognizable.

Shulchan Aruch (ibid.): One may not move an Aliyah ladder.

Beis Yosef (DH v'Rabbeinu): The Tur says that a big ladder, e.g. of an Aliyah, is forbidden. It seems that he rules like R. Tam, who forbids Aliyah ladders because they are big. This is difficult. In Siman 308 it seems that the Tur rules like R. Avraham, who permits even big Aliyah ladders on Shabbos! R. Tam forbids on Shabbos and Yom Tov. I say that the Tur rules like R. Avraham, like he connotes in Siman 308. Here he wrote that a big ladder, e.g. of an Aliyah, is forbidden. This is even like R. Avraham. All agree that a Stam Aliyah ladder is big, just R. Tam forbids on Shabbos and Yom Tov, and in Eruvin they permit a house ladder, which is not so big. R. Avraham forbids a big Aliyah ladder on Yom Tov, and permits on Shabbos. A house ladder is like a dovecote ladder. It is permitted on Shabbos and Yom Tov. However, the Rosh wrote that according to R. Avraham, one may not move our ladders on Yom Tov. This connotes that he refers to house ladders. Perhaps we can distinguish, and say that he refers to a ladder as big as an Aliyah ladder.

Mishnah Berurah (28): Some permit a ladder special to use in the house, which is often moved from corner to corner. It is not as big as an Aliyah ladder. It is not proper to fix the roof. One may move it like a dovecote ladder. Some are stringent. We permit only a dovecote ladder, which is recognizable. All know that it is for birds. A Stam ladder, even if it is small, can be brought near a ledge, and from the ledge he can go to the roof. L'Halachah, one may be lenient to move it in the house, but not in Reshus ha'Rabim.

Kaf ha'Chayim (39): R. Zalman forbids moving a house ladder in Reshus ha'Rabim, even if there is an Eruv.

Mishnah Berurah (29): One may alight on the ladder to his Aliyah or dovecote without moving the ladder. The Mechaber connotes that an Aliyah ladder is Muktzeh, but the Gra connotes unlike this. Stam Tiltul is permitted, but he may not move or tilt it for a use.

Shulchan Aruch (308:19): One may not move an Aliyah ladder, which is big and made to plaster the roof. One may tilt a dovecote ladder from place to place, but he may not move it from dovecote to dovecote, lest he do like he does during the week, and come to trap.