This is a very easy to do comedy routine with a twist. You show two pieces ropes, you choose one and the volunteer chooses the other.
You proceed to teach the volunteer how to tie a square knot on the rope. While you are able to tie the knot he is not able to do it. You can even slide the knot up and down the rope.
For the finale, you can actually pull the knot off the rope and hand it out for inspection.
This is a very well made square knot with an extra rope made from brightly colored soft crotchet material.