The Surgeon's Loop is a quick and easy way to put a loop in the end of a line. It's tied in the same manner as the Surgeon's Knot.
Double the end of the line to form a loop, and then tie an overhand knot at the base of the double line.
Leaving the loop open, bring the double line through once more.
Hold the standing line and tag end, and pull the loop to tighten the knot. You can adjust the loop size by shifting the loose knot before tightening.
Clip the tag end.