Everyone at some point has been in the position of going through a door that locks from the other side. How do you get back in? always be ready with a Loc-Stop on your keychain! print in very strong filament!! (carbon fiber PC or carbon fiber nylon highly recommended!) this model was tested. Instructions: 1.Stick the triangle part of the model into the hole thing on the door where the latch goes in. 2. Make sure it extends out on the locking side. 3. Close the door.