The Double Surgeon's Loop is a quick, easy way to tie a loop in the end of a leader. It is often used as part of a leader system because it is relatively strong.
Double the tag end of the line. Make a single overhand knot in the double line.
Hold the tag end and standing part of the line in your left hand and bring the loop around and insert through the overhand knot.
Hold the loop in your right hand. Hold the tag end and standing line in your left hand.
Moisten the knot in water and pull to tighten. Trim tag end to about 1/8 inch.