scifi "speed over the fence" is another airline term which is to do with landing performance.
Airliners are not mean to land on the numbers. The touchdown point is at a set distance down the runway with a nominated angled path down to it. When you are on this path then when you go over the threshold you will be at a specified height. This is referred to as the fence.
For departure there are also fences for take off performance which depend on if the runway is wet or not.
I have not on purpose given any hard numbers for these "fences". Like the 1.3 VSo which is also a airline reference speed number it isn't relevant to SEP aircraft.
It doesn't have anything to do with a physical fence on the airfield.