The purpose of the Shock Leader is several. The most important of which being to absorb the "shock" created by a surf-cast with 8ozs plus a piece of bait.
Generally speaking the normal shock leader that is used is 50lb test. Now with the variety available diameters of certain brands may differ.
The shock leader is almost always mono or another co-polymer line. Some see value in using flourcarbon. I am not one of those. Flouro is thicker, has more memory, harder to tie and is expensive at the rate that you will go through your shock. The most commonly used brands include the standards ANDE and Berkley Big Game.
Your shock leader should be at a minimum 3-5 wraps around your spool, plus the length of your drop. There really is no maximum length, but the longer your shock, the more likely you will have "guide slap" when casting.
The running line (coming from the reel) should be doubled. A knot made from 17lb or 20lb to 50lb shock will be less than the breaking strength of your running line if you do not double your line. The options available there are either to tie a bimini twist or a spider hitch. I prefer the bimini as the spider hitch does weaken itself over time and pressure. Learn how to tie a bimini or spider hitch. No knot will hold as well without having the running line doubled. I use a bimini to a no-name or Sosin knot.
1. Create a loop (bimini or spider hitch).
2. Insert your shock leader into the loop.
3. Wrap the shock 4 times around the loop.
4. Push the running(from spool) shock through the bimini to create a small loop. Once you do that, insert the tag(end) of the shock back through the small loop you just created with the shock.
5. Pull lightly on the running shock to remove the loop created in step four which will give you this.
6. Now here is the only tricky part of this knot. As with any knot, make sure to lube (SPIT) on it. The knot will not properly cinch down on itself without damage without some sort of lube. Hold firmly to the running line from bimini side. Hold firmly to the running shock (NOT THE TAG, ONLY FROM THE RUNNING). Pull against itself to tighten. The key I have found is that you have to pull quickly and firmly, do not walk the knot down. You should end up with this.
7. From there, this knot is secure. It should always be this small and the wraps should be touching, never over-laying. You can now trim the tag flush with the knot wraps themselves. Your end product should look like this.
You now have a completed shock knot/leader. There are quite a few knot combinations out there. I have found that this is the quickest and smallest while retaining near 100% breaking strength.
