The most common dropper knot but the length of dropper does have a tendency to tangle around the main leader.
¦ Take the main leader and cut off a length of say, 10 inches. Offer up the two lengths of line in the position you’d like to place the dropper so they overlap by several inches.
¦ Using both lengths, form a loop.
¦ Pass the tag end (loose end furthest from the fly line) through the loop three times before drawing tight. Remember to pull on all four ends to draw up the knot evenly.
¦ Having tighwtened, cut off the tag end pointing towards the fly line, leaving the other pointing towards the end of the leader as a dropper length.