How to prevent our new cat from opening the screen door (and proudly bringing half-dead lizards inside) without us having to constantly latch and unlatch the door. We needed some kind of self-closing mechanism to keep the door shut.
Wedge a flexible rod between the door frame and the door edge, as shown in Image 1. It acts as a spring to press the door shut. This one is too strong for our cat to claw open the door, but easy enough for us to open, walk through and let the door slide closed.
l lucked out with an old CB car antenna that worked perfectly with no modifications. Our door frame has U-channels all around to contain the ends of the rod so I was able to literally wedge it in place and make sure it worked without springing loose. You may need to secure the ends for your particular application. Your local hardware store or plastics store should have a variety of bendable rods or other materials that will work for this.
Caution: The rod will be under tension so be sure to wear safety glasses and be careful while installing and testing!
What began this project was Sammy the Cat clawing a hole through the original patio screen door. I re-screened it with heavy-duty "Pet Proof" screen which solved that problem, after which the kitty would just slide the door open. The battle of wits continues. No cat is going to make a monkey out of me!