I had kind of a weird problem with no obvious solution. My Air conditioning is somewhat unbalanced where one bedroom is far too cold and the adjoining main room is a significantly higher temperature. I have had to keep the door to this room closed as I have cats that get in this bedroom and cause problems and make a mess. So I wanted to somehow prop the door open so air can exchange but keeps the cats out until I rework the ducting somehow to fix this. Of course the first thing I do is go to Thingiverse and seek a solution and in short time I found the Ninja Lock! https://www.thingiverse.com/thing:1032595.

I printed that design and found some issues I didn't like with the print design/structural integrity and I wanted it longer. Also it scratched up my door frame pretty bad quickly. So I used the Ninja Lock as my source template and designed something very similar in Fusion360. I beefed the part up significantly, added fillets at all the sharp angle/weak spots, made it longer and thicker, and added a button to make it easier to push the lock open from inside the room since we are leaving it on all the time right now. Lastly I added some felt to the part that holds the door jam to prevent more damage. How awesome is this hobby?!!! A year ago I would have never thought I could see a design that was useful and then use 3d modeling software to completely remake it exactly as I want it and produce copies of it rapidly to address an immediate need.

The original designer meant it to be a child lock, I would not trust it for that personally since I'm pretty sure my 4 year old could bust through it but for my needs, cat sequestration, it works perfectly (see test subject alpha picture, AKA Rambo).

UPDATE I've added a second redesign that has an over-travel stop to protect the part that is most susceptible to breakage and beefed that area up a little. My first version was broken when someone pulled very hard. The first version works fine if you're careful, the second version is much harder to break.