644. How Something is Made a Base for Muktzeh

89:4 A vessel only becomes a base if the muktzeh was on it Friday at twilight. If the muktzeh was not there at twilight, but only placed there after Shabbos began, it doesn’t make the vessel a base and one may handle the vessel even with the muktzeh on it. Therefore, one may shake the table or the tablecloth to remove peels or bones so long as the table or tablecloth was not made a base to candles as was discussed in 89:2.

A vessel also does not become a base unless one intentionally put the muktzeh on it to remain there during twilight. If the muktzeh remained there simply because one forgot it, or it fell there on its own, then the vessel does not become a base.