We used a pressure gate ( the kind that is adjustable and stays put by pushing down on the handle to jam it into the space). It fit in our sliding door (against the framed and the side that didn't move). We never had any trouble with it and our door opened to nothing. It was a straight 4 1/2 foot drop straight down (there was no deck). The only person that almost fell out was my dad because the screen door came loose and he was using it for balance while he leaned out to toss something out the door. The kids all learned very quickly not to lean on the gate and by the time my youngest dd was 3 we stopped using it. She just stayed away from the door.
In our new house the gate will have to jam against the sliding door and the frame but same principal.
at 11:10 AM on Apr. 26, 2011