On my many travels around the ''Car-Park'' I have seen some of these strange-looking fence's but have never given them any real thought. That is very interesting...fascinating. So sad to know that there were people in serious pain, and dying on what is, and has been for a long time, your garden fence.
For what it may be worth, they appeared as a question on QI last night, with the explanation that they were stored in case of mass gas attacks, and not actually used as "proper" First Aid type stretchers, so don't think they symbolise some poor soul dying in agony. The explanation was that the steel would be easier to decontaminate than canvas stretchers, but as no mass gas attacks occurred they were simply used at the end of the War as easy replacements for all the iron railings that had been cut down at the start of the War. Ooops, beaten to it, but just to reassure our Little Friend!