Just like there’s Left/Right-sloping (material/tier) Wall, there should be a way to place fences on top of them.
My fenced walls often go up and down to adapt to the terrain inclination, and it doesn’t look good when fencing them and going up a level and fencing the upper level. If I just build a slope to make it look nicer (and still not good enough) then it becomes a risk to climbing intruders, if not then there is a whole wall height difference.