In The Riddle of Penncroft Farm, Lars's mother tells him he used to "bamboozle" Aunt Cass by pulling in the latchstring to lock her outside when she was hanging up the wash.
I happened to see a door opened (and lockable) by a latchstring at the Elvehoj Museum of History and Art in Solvang, California, recently. Of course, the hardware looks a bit different from that of 18th century English colonists in America, but the operating principle is the same.
The string would be pulled inside at night so that the door could not be opened. (Watching on a mobile device so the video doesn't appear? Watch it here!)