It's pluralia tantum. So one door is "jedne drzwi" - however weird it is to make a plural form of the numeral "one".
We have the same thing in Russian, for the word sutki, which means 24-hour period (a full day). The singular form is odni sutki, seemingly plural, similar to Polish jedne drzwi, there's no such thing as odna sutka.
Russian "door" dwier’ is singular and dwieri plural "doors," that's why I asked.
Wiktionary says that soski are rubber nipples - but in Polish sutki are actually human nipples ;)
Singular soska, plural соски /'SOS-ki/ are rubber nipples
Singular sosok, plural соски /sə-'SKI/ are biological nipples
By the way I heard more than once "Двери" applied to a single door. Like "Закрой двери" (shut the door). At least in places I lived.
Yeah I've heard that all my life too. Could it be an alternate case of дверь, like accusative maybe? I know it's an inanimate noun, so maybe it's left over from older usage. Or, you're right and it's just plural being used to refer to one door.