Make a loop in the end of one of the ropes. Thread the other rope into the loop, around the two pieces of the first rope and back out through the loop, the same way it went in. After you cinch this up, you can pull hard and you have successfully joined two very different ropes.
Last Updated: Tuesday, August 11th, 2015, Created: Tuesday, September 14th, 1999
Tying Knots -- Joining two different sized ropes