This is the 15146th most frequent Russian word.
полок
A shelf or bench in a sauna (banya).
In this case, 'полке' is the dative form of 'полка', related but different word meaning a shelf in furniture.
На полке в шкафу стояли книги.
Books were standing on the shelf in the cabinet.
Here, 'полок' (shelf) refers to the wooden plank structures in a sauna for sitting or lying.
В бане на верхнем полке приятно лежать.
In the sauna, it is pleasant to lie on the top shelf.
In this example, 'полоки' (shelves) refers to the constructions inside a sauna on which people lie or sit, emphasizing craftsmanship.