Daily Halacha - Shabbat Laws, 16 Iyar 5777

What is the law of a base for a forbidden object?

An object permitted to be moved on Shabbat, upon which the owners placed a muktzeh item before Shabbat with the intention to leave it there throughout Shabbat, is forbidden to be moved even if a non-Jew or a minor removed the muktzeh item from it, due to the law of "basis l'davar ha'asur" (base for a forbidden object).

Does a muktzeh object placed without the owner's knowledge on a permitted object turn it into a base for a forbidden object?

When someone places a muktzeh object on someone else's item, the bottom item does not acquire the status of a base, since a person cannot prohibit something that does not belong to him.

However, if one's wife placed a muktzeh item on his belongings, the permitted item is considered a base for a forbidden object and is prohibited to be moved, since one's wife is considered as an extension of himself [Chazon Ovadia 3, p. 137].

Courtesy of Daily Halacha - Ach Tov VaChesed