Which structure currently operates as a "virtual fence:"  Boarder Wall or Mexico-United States Barrier?
Mexico–United States barrier The Mexico–United States barrier is a series of walls and fences along the Mexico–United States border aimed at preventing illegal crossings from Mexico into the United States. The barrier is not one continuous structure, but a grouping of relatively short physical walls, secured in between with a "virtual fence" which includes a system of sensors and cameras monitored by the United States Border Patrol. As of January 2009, U.S. Customs and Border Protection reported that it had more than 580 mi of barriers in place. The total length of the continental border is 1,989 mi .
Suicide barrier A suicide barrier is a barrier on a bridge (often a so-called suicide bridge known for suicide attempts), observation deck or other structure designed to prevent people from attempting suicide by deliberately jumping. Many suicide barriers are tall and fence-like. But suicide nets, which extend horizontally below the bridge and preserve views outward, have been used on the Bern Muenster Terrace in Bern, Switzerland and the Cornell University campus in Ithaca, New York. In 2009 a barrier was built for the Humber Bridge, and in April 2017, California began construction on a $200 million mesh barrier beneath the Golden Gate Bridge.