I had an unusual requirement. Both my neighbors on this south side are uphill from me. A line of huge blocks of stone divides our properties. I wanted to be able to see the stones under the fence. I wanted air circulation so to prevent plant diseases. And I wanted to have access all the way to the stones so that I could cut out any seedlings that the birds and squirrels and wind plant there.
The solution was to make the top of the fence horizontal and let the bottom be open. The height of the fence matches the height of the fences each of my neighbors built. I hope my neighbor is pleased.