Rope geometry

... that is second to none:

You present a rope and tie a knot in it, forming a square. Immediately, you untie the knot.

Now hold the rope in one hand and the square knot in the other.

Then tie another knot in the rope, this time in the shape of a triangle!

Simply pull off the triangle as well. Now the rope passes through your body—it's simply pulled through from back to front—and finally, there's a circular knot.

Remove this one as well and hand both over for examination!