Years ago I had a dog that I needed to occasionally keep confined in the kitchen. No matter what I did, he would defeat it, and escape. I was in Walmart with the wife one night, and as we strolled through the store I saw the "kids" section. We had no kids at the time, but it sparked an idea. I found the baby gate section, found a good one, held it up to the wife and said "If this doesn't keep that son of a b!tch in there, then I'm stringin' barbed wire across the top."
My wife burst out laughing when she saw all the parents in the section stop and look at me, some of them aghast. I quickly explained it was for my dog and moved on.
The baby gate was unusually effective, mainly because once a dog has learned they can't get over it, they just assume they never can. I think they call this Classical Conditioning in psychology. As another example, the storm door that leads to my back yard is entirely glass, but the glass can be removed to install a screen. My dogs have lived with that glass door their entire lives, and one day I removed it to put the screen in, but before I did so, I ran an experiment. The dog was sitting next to me and I walked right through the door because the glass had been removed. There was literally nothing keeping you from leaving, you could feel the breeze and smell the outside...but the dog simply would not even try to go through. Over and over I did this. I'd jump through, reach back through and pet him, hold out a treat, call to him, had the entire family step through to the outside, but Classical Conditioning had wired his brain to believe he couldn't go through that door, so he never tried.
Anyway, back to the baby gate, it worked so well that even my Great Dane viewed it as an obstacle. She grew up with the gate, it gave her the impression it was impassible, and that stuck even when she was big enough to simply step over it. The pic below shows a typical stance she'd adopt when she wanted to come out. Even at that size, she viewed the baby gate as an impassible obstacle.
ocho place by
s s, on Flickr
Sorry to hear about your loss. I've had to put one down as well, and even when it's the right thing to do, it still sucks.