This is an interesting fence for many reasons. First it is at the top of the highest mountain in Europe, Jungfraujock. We are 11,333 feet above sea level and yes, it took us a little while to acclimate to the "thin air". But, surprisingly we were fine in short order. Second, this fence is movable ... moved to where it is needed because it has a very special purpose.
As the sign is telling you ... if you go past this fence, you may fall into a very deep crevice. One can only imagine how deep and thus nobody goes past the fence. So it doesn't have to be stable or strong, it just has to show you something you need to know :) Have a great "Good Fences" Day!