Mishnah: Beis Shammai: One cannot remove the shutters of booths on Yom Tov. Beis Hillel: It is permitted even to replace them.
Question: What kind of shutters are we talking about?
Ulla: The shutters of stores [portable booths that were used in the marketplace as stores]. 
Ulla: There are three cases in which the end was permitted in order to encourage the beginning of that thing. 1. Skins before the treaders (048). 2. The shutters of stores. 3. Returning the bandage on a plastered wound on Shabbos or Yom Tov in the Mikdash [when there’s a plastered wound, a bandage cannot be put on, lest one smear the salve. This is permitted in the Mikdash so that the kohanim can remove their bandages in order to do the avodah without chatzitzah].
Rechava quoting Rabbi Yehuda: [Rechava was much later than Rabbi Yehuda. He couldn’t even be quoting Rabbi Yehuda Nesiah. Some explain that he is actually quoting Rav Yehuda but because it was his primary rebbi, he called him Rabbi] another one should be added: 4. One who opens his keg or begins a dough on the Regel for the purpose of Yom Tov [when Jews were oleh regel, the din was “chaverim kol yisroel”. Although normally an am ha’aretz is not relied on to maintain taharos like a chaver, and anything he touches is considered tamei; on Yom Tov we consider all Yisroel to be chaverim. The law here is teaching that in order to make wine available on Yom Tov, we permit a keg opened on Yom Tov and touched by amei ha’aretz even after Yom Tov is over already. The same rule applies to dough]. This is in accordance with Rabbi Yehuda (053) who said “he may finish” [that he may finish whatever he started for Yom Tov even though it is no longer Yom Tov].
Challenge: ‘1. Skins’ is explicitly stated by the Mishnah?
Resolution: One might think Beis Hillel permits this because it is fit for use as a seat (40, 48, 51), and thus it would be permitted even if the animal was slaughtered before Yom Tov, this is why Ulla explains that “the end was permitted in order to encourage the beginning” on Yom Tov. 
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