Page 158 - Buck Tilton - Outward Bound Ropes, Knots, and Hitches 2 ed.

Take the end of the single loop down and around

the end of the double loop.

Bowline on a Bight: Step 4

Continue to bring the end of the single loop over
the knot that has now been created in the line.

Adjust the size of the double loop to the desired
dimension before tightening.

Double Bowline

A VARIATION OF THE BASIC BOWLINE THAT ADDS
SECURITY TO THE KNOT