The leader functions as the connection between the fly and the fly line. With a long enough leader the thick fly line lies outside a fish's field of vision and the terminal end is so thin the fish should not notice it.
Leaders are made of light, transparent monofilament material. They are also tapered, with a thick base called the "butt" section, and a thin terminal end called the "tippet."
Most leaders are between 7 1/2 and 12 feet in length. One of the primary reasons fishermen fail to catch fish is because their leader is too short. A longer leader is necessary whenever pursuing wary fish or fishing in extremely clear water. Only when fishing large streamers underwater is it advisable to use a leader that is less than 7 feet in length.
There are three main types of leaders: braided, compound and knotless. Braided leaders are popular in Europe and have a butt section made of braided line that some believe is easier to cast. Compound leaders are made from multiple strands of line of varying thickness, tied together to create a single tapered leader. Some claim that the leader's construction prevents drag, allowing an artificial fly to drift more like an actual insect on the water. The knotless leader is simply a single, tapered strand of monofilament line.
Tippet thickness is measured in X-numbers, from 0X to 8X. The higher the number, the thicker the tippet. You should carry spools of various-sized tippet with you to add to your leader as it becomes shorter due to changing flies or breaking off on snags. It is also important to select the right size tippet for the fly you are using. A good way to choose an appropriate tippet for a particular fly is to divide the size of the fly by three. For example, if you are using a #12 fly, 4X tippet would be best.
Article Written By Richard Hansen
Richard Hansen grew up and currently resides in Minnesota. He graduated from Dartmouth College and has traveled extensively in Africa and South America, including the Amazon jungle. He has worked as a wilderness guide in Yellowstone and northern Minnesota, and written for Fur-Fish-Game, Dartmouth Alumni Magazine and RascalHansen.com.