This is the easiest way to remember how to tie the alpine butterfly loop — a great loop knot that can be tied in-line and works for load in either direction. Easy to untie too. Forming it in-hand this way makes this knot quick and instinctive to tie.
Use the Alpine Butterfly in setting up a top-rope anchor: form a loop in your static line to clip in to when you go near the edge to set up. Use it to isolate a damaged section of rope.
This knot has the cool structure that is easy to loosen (like the bowline and sheet bend): the locking bight is angled across the loaded line so you just have to rotate it back to loosen the knot. This is shown at the end of the film clip.