Here is a part of James’ article on Leadcore fishing that covers the knot:
Getting Everything Set Up
Some people figure incorrectly that using lead line is somehow difficult or complex. Nothing could be further from the truth. Setting up a lead core outfit for trolling is very similar to preparing conventional gear.
First, load the lead line onto the reel. Begin by tying two over hand knots around the spindle of the spool.
Unsure the knot holding the end of the lead core is pulled down tight to prevent line slippage before proceeding further.
Begin winding the lead line onto the spool slowly ensuring that the line plays out evenly across the width of the spool.
Fill the spool to within ½ to ¼ inch of the rim of the spool. You’re leaving this room for a length of monofilament leader.
Attach a 25-50 foot length of 10# test mono (Trilene XT) as a leader between the lead core and the lure. To do this push the dacron sheath at the very end of the lead line now on your reel back approximately 4-5 inches to expose the lead filament inside.
Break off this short section of lead filament and discard.
The sheath of Dacron that you pushed back to expose the filament needs to pulled back into its original shape. You should have a 4-5 inch length of dacron at the end of your spooled lead line that does not have a lead filament inside.
Tie an over-hand (granny knot) in the dacron about one inch from the end. Pull this knot very tight.
Finish off by tying a standard or improved clinch knot in the monofilament line above the small over-hand knot you tied earlier in the dacron. Pull the monofilament down to the knot in the dacron and ensure that the knot in the monofilament is tight. Trim the tag ends off both of the lines and your done.
This method of linking a mono leader to the lead core line results in a very small, compact knot that offers little resistance as it moves through the water and also slides through the guides of the rod and onto the reel without hanging up.