I inadvertently left a sefer I wanted to use on Shabbos on top of my computer. Make I take the sefer off on Shabbos, given it’s not really a b’sis, I think. Can the rov please briefly review the practical rules of b’sis. Relatedly, I need a vitamin that is in a drawer that houses my money wallet. I can access the jar without touching the money or any other muktzeh item, ok?
An item will only be a bosis if it is supporting the item (the word bosis means base or support). Therefore if the sefer is on top of the computer, the computer is the bosis of the sefer and not the converse, therefore it is not a problem. Additionally even if the sefer was left underneath the muktza item, since it was left there unintentionally the sefer will not become a bosis.
Shabbos 142b, O:CH 309-4 M:B 309- 18, 20.