>> you have to have see through. you have to know what's on the other side of the wall. you could be two feet way from a criminal cartel and don't even know they're there. now we have equipment to take care of that, x-ray equipment, et cetera. >> what do you think about the importance of three sooe through? >> when i have a see through wall, sir, i know what's approaching before it approaches. we have great partners in mexico with law enforcement on that side. i can call them for assistance. i don't get the opportunity to get ahead of a threat if i can't see the approach. >> and what's the danger of not having the see through. >> we found smugglers were using the fence to hide behind, rocking our agents or large