Neat stuff! I remember reading about a type of door latch pioneers used to use in cabins that had a leather thong or rope poking out through a hole in the door. This allowed them to leave the door closed, but open it from the outside. To "lock" the door they would pull the cord into the cabin at night, and it was no longer possible to open the door. I never saw a drawing though, and can't for the life of me remember the source.
