A particular use of the expression "turn down"

I have just come upon the following sentence in a book:

"A page was turned down, as if to draw attention to some passage".

(The specific context is very simple: the character has taken a book and started reading it.)

As a non-native speaker, I am quite intrigued by the use of the expression "turn down" in this case. None of the Lexico definitions fits. Does it mean the page was "marked" by the reader somehow? Is it common to use "turn down" this way?