The border fence is a hot topic on the Republican presidential campaign trail.
Herman Cain wants to electrify the fence.
Michelle Bachmann wants a double fence and Mitt Romney wants to extend the fence along the entire southwest border.
There are 649 miles of fence along the U.S./Mexico border. The tallest point is 30 feet high, and the longest stretch 300 miles in Douglas, Arizona.
The fence is a patchwork of materials that serves as a timeline showing the evolution of the barrier.
"Every time we implement any new type of fencing we learn from the limitations of the last fencing that we had in place," says U.S. Border Patrol agent Colleen Agle.
In Douglas construction crews are replacing the oldest fencing.
"The first generation was a lot shorter so people did have a lot easier time climbing over it, and it was also just sheet metal so it was very thin," Agle explains.
Over time smuggling organizations have figured out ways to go over, under and even through the fence.
"These bollards that were cut last night, they attempted to bring a vehicle north," says Agle.
That vehicle filled with drugs ended up turning back when border patrol agents arrived at the fence after spotting the smugglers.
"This high ground here will give me the advantage and get other agents to get on the traffic as they come north" says Border Patrol agent Jaime Leos.
The oldest barrier along a particular stretch of border is known as a "picket fence" because of the white bars. Mesh was added later because people used to stick their hands through the bars, using them to climb over the fence, and then it would take just a few minutes to make it into town.
"We know that over time they’re going to defeat this fencing, this brand new fencing as well. But as of right now this is the best stuff we’ve got and it’s doing a much better job for us," says Agle.
It's doing a better job of slowing down illegal border crossers, giving agents more time to catch those who are not deterred by the fence.