1) If it's attached with hinges, it's viewed as something made to be opened and closed constantly, like a door, and the prohibition against creating a canopy wouldn't apply. 2) We saw that both building - ''Boneh'' - and dismantling - ''Sotare'' - are ''Avot Melachot'' (prototype prohibited activities); both setting up a canopy and dismantling a canopy are prohibited as derivatives - ''toladot'' - of these ''Melachot''. 3) According to the Mishna Berurah (315:48), this prohibition only applies to objects with wide openings. There are opinions among the Rishonim (early authorities) that the prohibition against creating a canopy on Shabbat doesn't apply to covers of ''Kelim'' (movable vessels or furniture), however, the Mishna Berurah 315:49 rules that one should follow the more stringent opinion in this matter, which is held by the majority of authorities. 4) It's only considered creating a canopy if there is a hand-breadth (9-10cm) of space between the content of the barrel and the covering; if, however, the barrel is full, there is no prohibition against covering it (Shulchan Aruch 315:13).

פי העשן ארובה אם הוא מן הצד שהסתימה היא כמו תוספת מחיצה מותר לסותמו אבל אם הוא למעלה אסור לסותמו בשבת וביום טוב משום דעושה אהל ואם קבוע שם דלת של ברזל סובב על צירים מותר לסתום דכיון שהוא קבוע שם הוי ליה כדלת הסובבת על צירים

1) According to the Mishna Berurah (315:48), this prohibition only applies to objects with wide openings, whereas covering vessels with narrow openings would not be considered creating a canopy. There are opinions among the Rishonim (early authorities) that the prohibition against creating a canopy on Shabbat doesn't apply to covers of ''Kelim'' (movable vessels or furniture), however, the Mishna Berurah 315:49 rules that one should follow the more stringent opinion in this matter, which is held by the majority of authorities.