I have the Purrfect Fence system that @DPRK linked to, but with straight bars to keep my dog in. I’ve had it about 6 years, about 250’ of it, and it’s still in perfect shape.
I can’t attest to how the bent arms keep cats in but the materials at least are top notch. And it definitely keeps my dog in (my dog doesn’t climb, he leaps).
I actually just bought some more material this past summer to add to my parents’ fence and they still have the same quality.
Eta @Richard_Pearse: but yes, the “scramble” sounds like it’s inelegant, but I just mean pawing/clawing up. Like I said “warped wall” style.
I don’t know, it’s not a claim I’m making, I just couldn’t sit by while you suggested the poster was “watching their video wrong. LOL” when you couldn’t even work out which bit of the fridge you were looking at.
.
Otherwise, for fun:
Like I say, a bizarre conversation. The fridge quite clearly has the doors facing the camera. I even provided a screenshot showing this. How you can possibly think the cat’s hind feet are purchasing the top of the door is beyond me.
I guess I mentally extended the fridge door line and merged in my personal experience of souvenir magnets going on the front of the fridge. I still think the cat found some purchase with claws/paws against the wall of the fridge and assorted decorations.
I do agree that those people have no idea how to do a fridge. Magnets on the side? Crazy stuff.
Purchase? With furry paws and claws against stainless steel. I don’t think so. The cat didn’t even dislodge any of the magnets-it didnt bear any weight on the decorations-none of which would have even given an assist to a 2 ounce mouse, much less a 10 pound cat.
So now we have an answer for the OP. To block the opening so a cat cannot escape will require 5 refrigerators with plastic pipes attached to the top.
I remember when I was living in Florida, covered patios and swimming pool areas were a thing – I’m talking enclosures. Though maybe expensive, the good thing is they keep your yard clean from leaves and debris.
Cat jumps 1.96 m (6’5") vertically.
Here’s another video of a cat in slow motion leaping to the top of a refrigerator. The door is perfectly smooth. The cat is pushing up with its hind paws but is not using its claws.
Well, the original context wasn’t ambiguous, it was a question of whether the smooth pipe overhanging the top of a 6-foot fence would work, since the overhanging pipe blocks the grab-and-scramble technique that the cats in these videos are using to get onto the fridge, it requires a clean jump to the top. But that was about 50 posts back, so maybe we’ve moved on from that.
That’s similar to the F1 Savannah doing 8ft that I posted upthread, or the caracals leaping to grab fish out of the air. But that height is the tip of its outstretched paw, which I think with that extended body is at least 12" above its center of gravity. What would that 6’4" correspond to as a ledge height onto which it could propel its center of gravity with a clean jump? I’d say more like 5 feet.
I would say the evidence so far suggests that the average cat could not get over a six-foot fence with an overhanging smooth pipe at the top. As you say, it would not be able to get sufficient purchase on the pipe with its forepaws, or use its hind legs for a boost. But I wouldn’t rule out an exceptional cat being able to clear it, maybe with a running start.
So make the fence 6’6". 
When I open the page it’s actually £23.63 for a 6x3m net. That’s still considerably less than $75, though. Mysterious.
When my cat had kittens, the kittens at 5 weeks old walked up and down a 4 meter, let’s say 11 feet, wooden wall using their claws.
Sorry, after looking at some pics, they were 8 weeks, and they used a tree to get on the roof. They walked up the wall, grabbed a branch by the roof, and got up on the roof. The opposite when they walked down.
I’ve been thinking about it (even though I’m sure some bigger brain people already did/do) but I realize that as long as the cat’s front paws have purchase, directly pushing off with the back paws horizontally can be converted into vertical movement using the front paws as a pivot. It doesn’t need to push up/scramble exactly.
The second video I linked to shows the cat’s forepaws don’t even need purchase. The cat leaps up, plants its hind feet on the vertical surface of the door, and then pushes up with its hind feet so its outstretched forepaws reach the top of the door. Then it pulls itself up with its forepaws while pushing up again with its hind feet. It’s not scrambling at all, but rather bouncing off its hind feet to reach the top.
The cat leaping up the refrigerator with the magnets does exactly the same thing, although its harder to see at natural speed. The hind feet hit the door first, and then push up before the cat has its forepaws on the top.
You’re right. There’s probably a few ways a cat can do it though.