Page 110 - Peter Randall "The Craft of the Knot.."

STEP 2 Tighten each Overhand by pulling on the two standing parts,
so that the two ropes are held firmly together.

STEP 3 Pull the two ropes apart so that they form a circle, tightening
each knot.

The Fisherman’s Knot is difficult to untie and will work best when tied

in small cordage. It is often chosen as a secure way to join two small
lines of similar size.

DOUBLE FISHERMAN’S KNOT

The Double Fisherman’s Knot is a bend tied in the same manner as the
Fisherman’s Knot, with two Double Overhand Knots in place of the
regular ones.