More details about the The Surgeon's Loop
Uses: The Surgeon's Loop is essentially a Double Overhand Knot. It tied can be tied quickly and easily in the end of a line. It is often used to make a "Loop to Loop" connection or to create a loop which allows the artificial lure or fly to move naturally.
Tying it: It is tied in the same way as the Double Surgeon's Knot.
Alternative: An extra turn can be used to create a Triple Surgeon's Knot. However, this provides minimal additional benefit and does make the knot bulkier.
Advantages: The advantage for this knot is that is reliable, easy to learn, and some sources claim that it retains a high proportion of the rated line strength.