Indesign and "overprint"

I have the german version and there it is called "überdrucken. "Konturen überdrucken" would translate as "those contures shall be overprinted by something" but "those contures shall overprint something" could also be the meaning.

So, if you have two rectangles, a blue one below and a red one above: and you want the red rectangle to print over the blue one: which one should get the "overprint" checkmark:

a) the below one, because it will get overprinted
b) the above one, because it will overprint
c) both?