I want to let my cat in, but not let them go out again. Can a PlexiDor do that? Yes, the small PlexiDor intended for cats and small dogs has several settings on the lock. The door can be set to: Open from both inside and outside Be closed from both inside and outside Open in one direction only That is, you can set it to allow your pets to come in, but not go out again. Or, allow them to go out, but not come back in.