On Friday, December 2, 2016 at 4:03:27 PM UTC-8, John B. wrote:

I seem to remember that in one location the Immigrations service
discovered a tunnel dug under the border to facilitate travel. Will a
"wall" prevent tunneling?

There have been MANY tunnels discovered. As well as a submarine. The drug business is a half trillion dollar business counting all of the illegal drugs consumed. These are not used to move illegals into the country since that would lead the cops to these transfer points.