the wife of Nowak would be "NowakOWA", however if Nowakowa were to be unmarried, it would be "NowakOWNA", with the final "o" having a hook on top
Officially these are no longer used, ime they're used mostly ironically or insultingly (I've only heard very old people use them unironically).
In modern Polish the difference is syntactic rather than morphological so that female last names ending in a consonant don't decline.
Widziałeś Nowaka? (Nowak is a man)
Widziałeś Nowak? (Nowak is a woman)