Once your backing and fly line are taken care of, it’s time to think about your leader, starting with the butt section. Probably the most common and, luckily, one of the easiest loop knots to use in the butt of a leader is a perfection loop. The perfection loop can be tied very quickly and is a pretty-small finished knot, which means it can pass through the guides easily. This is good since it’s the first knot of your leader that will do so when you have a fish close at hand. When the perfection loop is tied properly, the tag end should extend perpendicular from the loop.