My Sena, who is my perpetual 2 year old, can open the screen door and will let Lily, the puppy, out. When it's ok for Sena to go out, but not Lily, I loop a lanyard (saved from a rally name tag) thru the hand hold next to the door, out the open slide space and clip the metal piece to the door hardware on the outside. That way Sena can go in and out, but Lily can't. It's easy for me to unclip when I want out and I can also secure the screen door from the outside if I want to keep Lily in.
Barb (RVM18), Sena (capuchin monkey, RVM Head Mascot) & Lily (Maltese/Yorkie)
2011 Shasta Cynara 230F & 2012 Smart Car toad, 272 watt solar system
The Journey is Our Destination. Full-timing since 5/18/2011 and loving it.