The ones with the see-thru bottoms are failures.
Launch a weighted rope over the top and down the other side. Tie it around the see-thru support and you can scale over the wall easily.
The ones with a flat top fail also as a grappling hook can attach to them.
The ones with the rounded top and solid walls are best to prevent easy scaling
"The ones with the see-thru bottoms are failures."
Customs and Border Protection really like the see-through (bollard) designs, so they can see when folks approach the wall from the Mexican side. People trying to cut holes, or even trying to scale, need some time to bring their tools into operation and work. They are much less willing to do it where they open to observation. Eighteen foot Bollard barriers have been pretty successful so far (compared to other existing designs), but some young men (drug mules) have gotten good at scaling them.
A second barrier on the North side of an Enforcement Zone (no-man's land) could be a solid wall, that blocks them from seeing where the cops are.
Two 30 foot barriers (high as a three-storey building) makes it super challenging. Only fit young men stand any chance, and they are limited in what they could carry, or what tools they could bring for the second barrier. Add to that the much greater chance of being caught (or badly hurt in a fall), and few will try it. The Border patrol in such areas will be like the old Maytag repairman, with little to do.
”The ones with the see-thru bottoms are failures. Launch a weighted rope over the top and down the other side. Tie it around the see-thru support and you can scale over the wall easily. The ones with a flat top fail also as a grappling hook can attach to them. The ones with the rounded top and solid walls are best to prevent easy scaling” You said exactly what I was about to say. I like the rounded top because it would make it much more difficult to grasp with anything, but the see-through slats at the bottom negate that for the very reason you mentioned. I would make the wall solid from top to bottom, with the rounded top, and then use technology of one form or another to keep tabs on what is happening on the other side. If the military can detect an approaching UFO buff heading towards Area 51 using buried sensors, etc., then this shouldn’t be that difficult.