The Carrick Bend (also called Sailor's Knot, Josephine Knot, Fisherman's Bend, or Anchor Bend) is a strong, secure knot that can be used to join two ropes / lines of different construction. It is particularly appropriate for very heavy rope or cable that is too large and stiff to easily be formed into other common bends. This knot does not easily slip or jam, even if the rope is wet, and it is fairly easy to untie. The knot's smooth curves put as low a strain as possible on the line.
To Tie a Carrick Bend:
Make a loop with the first rope.
With the second rope, lay over the loop, go under the long end, over the short end...
...under and into the loop, over the long end of the first rope, under and exit the loop.
Tighten the knot by pulling on all four ends equally so the knot cinches down equally.
When the knot of the Carrick Bend comes tight, it will look like this.