I have one security bar that prevents the door from sliding open. However, the issue I had with that was that if someone were to be crafty, they could easily use a hanger or something like a slimjim to get inbetween the frame and pry the bar up...I tried it, hence, the fear...
To bulk that up a little, I used a simple screw and stuck in the tracks of the sliding door. It's out of view and jams the door if the bar is removed. With a good forceful push, assuming someone has already pried the bar up, it probably could be overcome. However, I'm comfortable that would require a lot of noise and I'd be awake at that point.
Finally, my smoker and mountain bike are against the door on the outside patio. Just a little enhancement to cause more work/noise. Old smoker and $2 bike so if they go missing, I have a reason to go shopping.
