The primary use of a bowline on a bight is to form an emergency bosn's chair. This is used for hauling people or objects up and down very steep or vertical inclines. The two loops go around the legs to support the majority of the body's weight. If the person being hauled is unconscious or injured, a butterfly knot large enough to go around the upper torso will hold them in an upright position so they cannot fall out. Be under no illusion that this is a comfortable way to ride. The rope has a tendency to cut off circulation in the legs but it will safely bring somebody where they need to be to get help. Put a loop over each leg and slide the knot as high as it will go. If you have anything to use for padding, slip it between the rope and the backside of the legs. The smaller the rope, the more important this padding becomes.
Begin by forming a fairly large bight in the line where you want your knot to be.
Form a round turn in the standing part of the bight where the standing part comes off the loop on the underside.
Grasp the bight at its furthest extremity so that both sides of the bight are equal (unless you want uneven loops in the finished knot).
The bights extremity becomes the new bitter end, poke this bitter end up through the round turn.
Open the bight where it comes out of the round turn (This is no rabbit coming out of a hole and running around trees. This is the mythological dragon that swallows its own tail.) Take this open eye or maw around both loops and the round turn.
Holding the original bitter end and standing part in one hand, draw the slack into the two loops and allow the round turn to be drawn snug about the bight.
This knot can be tied anywhere in a line including the middle and can be used anytime you need two loops in a line for hauling something, or someone, or as tie points.