The double fisherman's is a great knot for tying two pieces of rope together, and often used by climbers. I seem to recall when we tried to use it previously, we had difficulty with novices tying it. Ended up using the regular 9single) fisherman's knot. Not quite as secure, but easy to tie. Will have to play with some illustrations and give it another shot. I know it works great on braided line, not sure how well for monofiliment.