I'd like to see a "wall" constructed along those sections of our border deemed the most porous. A "wall" doesn't necessarily mean a physical barrier. I've lived and worked along locations of the Arizona/Mexico border. Both remote and urban areas. I've hunted, fished and ridden a little puffer of a motorcycle along miles of the border. A lot of the more isolated regions act as a sieve. Evidenced by discarded backpacks, water containers, bicycles, deflated rafts and clothing. A "wall" or the means to HALT the crossing of undocumented access to this country is essential. My concern that a "wall" will not only thwart undocumented entry it could be used to HALT a good citizen freely leaving at will. Remember that structure called the Berlin wall? When there's only one key a locked door keeps out intruders as well as inhabitants in. We need to devise more than one means or key to border security.
Sounds alot like what I and alot other GIs and West Germans and Brits trained for back in the eighties.
I'm sure our young men and women can dust off the old play book and set something up. Just one word of warning though. If it moves, it dies is how that works.