[caww]

No to concrete....border agents need to see through the wall so the people can't bring up vehicles and ladders unseen from the other side.....this is the best type...

[chris37]

No sale. This is insufficient and ineffective.

If one wants to see what is on the other side of a high concrete wall, one can stand on top of said wall and look down. One can further place cameras along the top of the wall and monitor them from a remote location.