i don't get how a wall solves this.
They'll start building "wall kits" with a nice ladder + rope for getting down. They'll stack up dirt piles to the top. They'll blow it up. They'll start fires and leave bodies all over it. Think of the horrors of such a wall.
BETTER SOLUTION is to make the illegals leave... fine anyone who hires them or rents to them, and offer a $5k reward to anyone that turns in an illegal. Watch how fast their legal friends drop a dime on their asses. And for the border itself, use technology to pick up the people wandering in, AND drop them BACK OFF someplace much further south... or even on the other side of the planet! If illegals knew thye'd be dropped off in Africa or India, for example, they'd think twice about that shit. Some shithole like Yemen would be happy to accept illegal aliens at a cost of $100 each lol. Ship em over!
A wall is low tech and stupid, designed for simple people that see a wall as invincible. A wall can be climbed, folks. Stop the illegals in a dozen smarter ways!