A Vernacular Fastened Door is a door used by members of V.F.D. to seal until the correct set of words is inputted into the locking device.
The Baudelaires first encountered such a door within the Mortmain Mountains, and with the help of Quigley Quagmire's commonplace book, were able to enter the correct phrases: "Sir Isaac Newton," the name of the scientist most widely credited with the discovery of gravity; "Panthera leo," the Latin name for the Volunteer Feline Detectives; and "A rural life of moral simplicity, despite its monotony, is the preferable personal narrative to a daring life of impulsive passion, which only leads to tragedy," the central theme of the novel Anna Karenina by Leo Tolstoy. The door was an entrance to the V.F.D. Headquarters in the Valley of Four Drafts in the Mortmain Mountains, the second-to-last safe place for the volunteers of V.F.D.
Another Vernacular Fastened Door was placed on the door of the Hotel Denouement's laundry room by Sunny Baudelaire at the request of Dewey Denouement. The door was a decoy to make the villains believe that the Sugar Bowl was located inside. After the Baudelaires were manipulated into helping Count Olaf open the door using Dewey's clues, they found that it was not inside.