Lets see if I can explain this.
You start with a overhand knot (I take the tag under twice as it helps the first knot stay tight a little better)
Then take the tags and tie another overhand knot but on the opposite side of the string just to one side of the original material. Continue with a series of overhand knots each alternating on opposite sides of the sting, and right next to the last bit of material until you have approx 3/16" worth of knots. Now tying off is something I still havnt mastered, but what I do is tie 2 back to back overhand knots (again take the tag thru twice) and cut the tails off with approx 1/4" left.
If the material is B-50, you can take a lighter to the tails and as they burn almost to the end, press them with you finger so they "melt" onto the knock you just made.
Hope that helps, but if may have just confused you more, I confused me just typing it...LOL