Linking Rope Loops (Wool)

The magician shows three different coloured ropes (Blue, Red & Green) and calls two spectators onto the stage. He gives each a colour rope of his choice. The magician asks the spectators to tie each one in a circle with a genuine knot and he too does the same with his piece of rope. Without switching the ropes or tampering the knots, he proceeds to link the solid rings of rope. Finally, the spectators are allowed to untie the knots and verify that they (knots) are genuine.