Brilliant! I’ve been thinking about how to lock the latch internally and I think you hit the nail right on the head. I believe that I’ll be doing something similar. Thanks for sharing!
Great Idea, however, I wanted something even easier. I bought a square dowel, cut 2 16″ pieces and put it under the door mechanism so the handle can’t be turned. Easy peasy. I also lock one door once I know I’m in for the night.