The Fisherman's bend is similar in principle
to the Uni knot. It's an excellent knot for joining mono over
about 40 lbs breaking strain.
When
joining lighter line use a double Uni knot by making five turns
rather than the two turns shown. If joining a heavier leader
to a lighter mainline, make five turns with the lighter line
to make a combined Fisherman’s bend / Uniknot.
