Well, unless the sound created by opening a door is a voice saying "creek- a stream or channel of water" I'm guessing they meant "creak". Though that's not as good as the Winnipeg Transit sign at Assiniboia Downs stating "Assiniboine Downs". That one is worse in my books. You'd think the people at ASD would at least want to get it changed.
Maybe "creek" comes from the same cartoon sound effects dictionary as "vroom," "vrooommmm" and "rrummf!"