Responsa על שבת 19:16

After close scrutiny, I say that carrying a parasol on Shabbat is not merely a teaching for the pious, and one who guards his soul will distance himself from it. Nevertheless, in my humble opinion, it is not what the eminent sage thought, for a melakha that does not correspond to the Tabernacle service has no liability on Shabbat. This is the formulation of the Yerushalmi [Shabbat 52b] at the end of chapter “Klal Gadol”: “What is the binyan (construction, one of the melakhot) that was in the Tabernacle? They would place beams on their bases. But wasn’t that temporary (lit. “for an hour”)? R. Yose says: Since they would travel and camp in accordance with God’s word, it is as though they were camped forever. R. Yose b. Bon said: Since the Almighty promised to take them into Eretz Yisrael, it is as though it was temporary—thus he says that temporary binyan constitutes binyan; thus he says that even irregular binyan [constitutes binyan]; thus he says that even if it is placed atop something else [it is still binyan]; thus he says that even binyan atop vessels (constitutes binyan). [No]—binyan atop bases is like [building on] the ground.” Maimonides likewise rules in Laws of Shabbat 10:12 that binyan atop vessels does not constitute binyan, and Magid Mishneh explains that it is dissimilar from the Tabernacle since the bases were akin to the ground. Magen Avraham cites this at the end of [Shulhan Arukh, Orah Hayim] §315. This Yerushalmi is cited by Rashba in his novellae on Shabbat, chapter “Haboneh” [102b, the end of s.v. “hai”].