Beis Shammai: A ladder cannot be moved from one dovecote to another. Beis Hillel permits this.
Rav Chanan bar Ami: If the ladder is on private property, everyone agrees it’s permitted.
Challenge: Didn’t Rav Yehuda amar Rav say “Any case the Chachomim forbade because of Maaris Hoayin, appearances sake, it is forbidden even in a hidden chamber”?
Resolution: Rav Chanan can explain that this matter is debated by Tannaim as in the following Beraisa: [If one’s clothes got wet on Shabbos] he may hang them to dry in the sun, but not in public [lest people think he washed them out on Shabbos]. Rabbi Elazar and Rabbi Shimon prohibit this. [So Rav would be following Rabbi Elazar and Rabbi Shimon but Rav Chanan’s explanation is in accordance with the opinion of the Tanna Kamma].
Others Say:
Rav Chanan bar Ami: The debate between Beis Shammai and Beis Hillel is only in a private place. Beis Shammai applies the principle of Rabbi Yehuda amar Rav and Beis Hillel do not. But if the ladder is in public, everyone agrees that it’s forbidden.
Challenge: It seems then that Rav holds like Beis Shammai?
Resolution: This matter is a debate amongst the Tannaim [as mentioned above. Rav holds that we rule like Rabbi Elazar and Rabbi Shimon. Only, Rav Chanan holds that there’s a distinction between a public and private place, he will hold that Beis Hillel follows the Tanna Kamma].
Our Mishna differs with this Tanna:
Beraisa: Rabbi Shimon ben Elazar: Beis Shammai and Beis Hillel agree that the ladder may be moved from dovecote to dovecote. The question is only whether the ladder may be put away afterwards. Beis Shammai: It may not be put away. Beis Hillel: It may even be put away.
Rabbi Yehuda: This is only said regarding a smaller ladder, but everyone would agree that a ladder which is used for roof repairs, is forbidden.
Rabbi Dosa: It can be inclined from one window to the other.
Acherim from Rabbi Dosa: If it is carried in an unusual manner with constant stops, it is permitted.