A Shock leader is a piece of heavier monofilament or fluorocarbon tied to the (usually lighter) main line to keep fish from breaking the line. There are many knots to join a heavier piece of line to a lighter one. For joining mono to mono or fluorocarbon some of the knots include the surgeon's knot, blood knot, and the uni to uni knot. For joining mono to braid the best knot to use is a double uni knot (This is where you double the braided line before tying the knot). Often for offshore fishing when trolling at high speeds with braid, a mono shock leader of 50 ft. or more is used to absorb the "shock" of a hard striking fish.
List other fish you have caught using this rig.