This routine is comprised of five different effects:
 
A knot appears on the rope
A loop penetration
An almost visible melt-through
A ring is placed onto a rope which has a knot tied in it. Suddenly, the ring appears tied inside the knot
The rope is twirled in the air and a knot is tied around the ring. The ring is removed leaving the knot on the rope!
 
Complete with a plastic ring and a length of rope.