“I like the ones with the tube across the top.
NOTHING to get a purchase on.”
I visited Berlin back in 1971 when the wall was still up. The old wall was made of brick. The top surface was flat with shards of glass cemented into it.
The new wall was much taller, made of solid cement with a rounded top like you see in one of the samples...the “tube” on top. They said there was no way of gripping it to climb over. When I saw the one in the photo, I thought of East Berlin.
That tube on the top is counter productive IF there are slots/slats down lower through which a rope could be passed.