The Double Bowline Knot is sometimes used as a "tie-in", to attach the rope to the climber's harness. The Double Bowline has the same strength as a figure eight knot but is simpler to tie. As the rope wraps around twice, the double bowline knot is more secure than a regular bowline knot.
To Tie a Double Bowline Knot:
Form two loops and thread the tie in point (harness, whatever).
Weave the rope back through the loops, around the main line.
Weave the rope down through the loops again.
Wrap the tail as shown.
Finish with a stopper knot to ensure there is no slippage.