Jackson: (after falling through a wall) Ow.
McKay: Controlled magnetic harmonic resonance.
McKay: Apparently Tesla was close to something like this before Edison trashed his lab.
Jackson: What are you talking about?
McKay: That wall was specially designed to destabilize when bombarded with a very specific harmonic resonance. That's what the tones were. And the strong magnetic properties of the particles is what keeps the door from just crumbling to dust. It's a great way to hide a door, because, you know, if you're looking for a door to, uh, open, it's never gonna be found. It's like PolyGram, but better, because it's solid mass until the tones are played.
Jackson: Right, so you could have just told be to walk through the door when you did.
McKay: I could have, yes.