First of all, the knot (nexus/tangle/foobaz/whatever) will need to move either inwards or outwards due to it never being in pure wallplane, ever. (Otherwise the heads would collide.)
They will meet at some angle, either outside or inside your arms. Once they do that, to undo the knot, move it to the opposite. (For me, I almost always do it outside to inside.)
Will try get a diagram up in a couple days, but this computer does not have anything worth using, sorry.
And, like I said, the tech section should have this.
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'We're all mad here. I'm mad, you're mad." [said the Cat.]
"How do you know I'm mad?" said Alice.
"You must be," said the Cat, "Or you wouldn't have come here."
- Lewis Carroll, Alice's Adventures In Wonderland