Here is a video showing the brainteaser in its entirety:
Step 1: What You Need
1)A rope, string or necktie (pick one)
2)At least two fingers on each of your hands :)
3)At least one person that you can ask to try to perform the trick. I like to refer to this person as "the victim".
Step 2: The Challenge
Step 3: The Execution
1)Cross your arms without touching the tie at all.
2)With your arms crossed, grab each end of the tie using your index fingers and middle fingers as "grabbers" or claws, if you will:)
3)Simply uncross your arms while you hold on tight to the ends of the tie. A knot will automatically be created when you do this.
Step 4: The Aftermath
Have fun and enjoy this. Thanks for watching!