This is the 14719th most frequent Polish word.
półkach
"Półkach" means "shelves" in English (locative case).
In this sentence, 'półkach' refers to the locative plural form of the word 'półka' (shelf), indicating the location of the books.
Książki na półkach w mojej bibliotece są bardzo dobrze uporządkowane.
The books on the shelves in my library are very well organized.
Here, 'półkach' is used in the locative case to describe the position where the fruits were found.
Na półkach sklepu znalazłem świeże owoce.
I found fresh fruits on the store shelves.
The usage of 'półkach' again employs the locative case to specify where the tablecloths are situated.