I’m sure you’ve seen them… 6’ chain-link fences with a relatively short (15" or so) barbed-wire section on top.
The barbed-wire section is usually angled. I assume this is done to make it more difficult for someone to traverse over the fence. But I would guess the difficulty of traversing the fence would depend on the direction of the angle relative to the person; if the barbed-wire section were angled toward the person, it would be much more difficult to traverse.
With this in mind, I would think a building would always angle the barbed-wire section away from the structure it is protecting. That way, it keeps people out. Yet I see many buildings with the barbed-wire section angled in. It looks like they’re trying to keep people in! Why do they do this? Did the fence installer screw up?