Question: How can one prove one's point from Mar Ukva, who was Amora?

Answer: We are forced to hold like mar Ukva, since without his explanation, we would not be able to establish the Mishnah in 'Lo Yachpor'.

Question: But the board is needed for itself, and any K'li that is needed either for itself or for its location, may be taken even it is normally used for an Isur?

Answer: The Gemara in Perek Kol ha'Keilim (Shabbos, Daf 123.) establishes this case by Muktzah that is valuable (Machmas Chesaron Kis), which everybody agrees is Asur, such as 'Sichi, Ziri and Mezori' (three expensive dyeing or weaving implements) over which people are fussy.

Conclusion: And even Beis Hillel, who permit it, that is specifically on account of Simchas Yom Yom Tov, as the Gemara explains there.

Refuted Reason: This is not because roasting requires salting, as Tosfos explains in Chulin (Daf 111.) ...

Reason: But because it was customary to salt, in order to give it more taste.

Minhag: And likewise the prevailing practice is to act subtly (and roast) and eat a little of the chicken, and then eat the liver.

Reservations: However, Rabeinu Shmuel used to say that this is only permitted prior to eating, but not after eating.

Explanation #1: Rashi cites some commentaries who explains that Rachba used this Lashon because he was uncertain as to whether he heard the statement from Rebbi Yehudah Nesi'ah or from Rav Yehudah.

Refutation #1: This is not correct however, firstly, because Rachba lived in Pumbesisa, and there is no indication that he ever went to Eretz Yisrael.

Refutation #2: And secondly, the Gemara in Pesachim (Daf 52:) says about somebody else that he particular when quoting the words of his Rebbe like Rachba from Pumbesisa'.

Reason: And if Rachba was not sure from whom he learned a particular piece, then the Gemara there ought to have rather said 'who even cited the sources of people of whom he was not sure', like the in Chuli Gemara says in Chulin (Daf 18:0 in the Sugya of 'Mugremes'.

Explanation #2: Tosfos therefore explains 'That he referred to Rav Yehudah as 'Rebbi Yehudah' because he was his Rebbi Muvhak (from whom he had learned most of what he knew).

Conclusion: And when the Gemara says 'That he learned a statement from him', he is referring to what he said 'Satav Lifenim mi'Satav' referring to the benches as 'Satav' and not 'Istevanis' (which is what the Tana called them), because that is what he heard from Rav Yehudah, and he did not wish to change from the wording that his Rebbe used.

Clarification: Because we Pasken that there is no Isur of building and demolishing when putting together or taking apart unless one actually constructs a K'li, in which case one is Chayav because of Makeh ba'Patish, or unless one builds on the ground

Clarification (cont.): As the Gemara says in Shabbos (Daf 102.) 'Someone who builds even the smallest amount is Chayav. Therefore, it teaches us that it is forbidden.

Question: But we do indeed Pasken 'Ein Binyan u'Setirah be'Keilim'?

Answer: It is nevertheless Asur (mi'de'Rabbanan) in case one comes to tighten it.