Before I built a wall I’d ask to know
What I was walling in or walling out,
And to whom I was like to give offense.
Something there is that doesn’t love a wall,
That wants it down!

From Robert Frost, “Mending Wall.”

Walling out: I don’t need to tell you if you’ve been following the news about Mexico.

Walling in: Check this link. And no, I’m not just piling on Donald Trump. Obama had plans underway to do what Trump is planning.