I saw the East German border up close and personal in the late 1970's.
They used various fences, tank ditches, mine fields, dog runs, towers and troops.
History can vouch for how effective it was and how many people died trying to get out.
After every big storm the GDR would go out there and roll over the mines and blow them up. Then they'd put in new mines.
There was a simple chicken wire fence along most of the sector I was on ~ ON OUR SIDE. It was there as a safety device. You didn't want to get any closer to the border than that chicken wire fence because there were MINES on the other side, and if one went off you could get injured. Plus, sometimes those mountain storms were bad enough that the mines washed out of the zone ended up on our side. There were some "divots" where they'd run the fence back further up the hill so we'd know the area beyond wasn't safe even though it was well within the American zone.
The German border patrol had nominal command over us concerning where we would go ~ many times we'd walk along with them and they'd discuss the mine fields, the loose mines, and that fence.
While there a VOPO tried to escape in the zone up near Hof. He ran across the minefield and missed all the big ones, but he hit a couple of little poppers ~ then one of his guys shot him (for the reward), and the Russians took a couple of days to retrieve him (with a steam roller).
I don't care who you were ~ our guys, their guys, border patrol for GDR or West Germany, or the Russians, or just tourists, spies and others who ended up around there, YOU WERE VERY CAREFUL.
Mines have no conscience and are unrelentingly cruel.
I've seen it. Done it. Been There. A mine field would work quite well. They don't even have all that expensive a maintenance cost ~ and you can put them in the mountains ~ 'cause I've done duty in the mountains with a minefield in front of me.
They are just nasty as all get out and send a clear message ~ get a tourist visa and take the plane to Phoenix!
Comprehensive immigration reform requires a fence, maybe a mine field or two, AND some serious evaluation of visa holders as they enter at our airports. Right now we depend on the consulates abroad to control the visas ~ and they clearly do a poor job. 40% of our illegals are people who entered legally and overstayed! A little interrogation at the airport as they come into the country would help control that. We could use computer systems to back us up on that ~ match faces, pull up criminal records, medical records, all that stuff ~ see what's up.