[euram]

the border wall should be topped with a coil or two of concertina wire.

[BeauBo]

"the border wall should be topped with a coil or two of concertina wire."

Ladders with a rope to descend are the likely way to get past the new 30 foot barriers. Concertina on top would really make that much harder. Concertina could probably be added later where needed, at reasonably low cost.