Middle Son has always been a climber. Even as a toddler, as soon as he could get his fingers on top of something, he'd climb onto it. Somewhere there is a picture of him curled up asleep on top of the refrigerator like a cat. That happened before he was three.
The fall after my divorce, Middle Son grew tall enough that he could get his fingers on the top of my backyard fence. And as soon as he got his fingers on it, he started climbing over the fence. Usually he just went around to his favorite shrub in the front yard and started pulling leaves off of it. But I wasn't confident that it would stay that way.
I became very careful about watching him when he was in the back yard. Pretty quickly he stopped trying to climb over in any of the spots where I could see him. Unfortunately, there was a blind spot behind the garage where I couldn't see him.
So I bought a surveillance camera that hooked up to my laptop. I put it up on the side of the house where it covered the blind spot. The first time I saw him starting to go over the fence, I ran out into the back yard calling for him to stop. When I got around to where I could see him, he was turning around slowly and staring. His body language and expression said very clearly "how did you know what I was doing? How did I get caught?"
When I moved to my current house, I didn't bother to set up the camera. Shortly after we moved in, we got Willow, his service dog. Now I tether them together and she makes sure he doesn't go over the fence.