A good leader must be thicker where it joins the line and with a degree of stiffness. A limp or soft leader will not lay out straight and hence impedes a nice presentation of the fly. The diameter of the thin end, or tippet, is varied and is chosen according to the conditions.
The strength of the outfit is completely reliant on the breaking strain of the tippet, being the thinnest part of your rig. The size is usually indicated by a number and the letter X. Tippet size also influences the delivery of the fly and a good balance is required between the weight of the fly and the diameter and weight of the tippet.
Two types of leader are available, being the knotted and the knotless. The knotless is a single piece of monofilament tapered during manufacture, the knotted type is constructed using various pieces of monofilament knotted together, the latter being the most popular due to its delivery capabilities. The leaders are usually manufactured in 2.3m and 2.7m lengths.
Although the previously mentioned number and X method of identifying leaders is used, the more common method of ordering leaders is to quote the length and breaking strain. Length is important as a leader which is too short will not present properly and will make the fish suspicious. The butt of the leader should be easy to attach to the fly line and usually consists of a loop. At the end of the day’s fishing the leader will more than likely be much shorter than at the start. The making of leaders from monofilament is a skill and there are as many different styles as there are fishermen, being made for the conditions encountered and to suit the other equipment of each angler.
The abovementioned are those that are commercially available. To construct your own is a very valuable learning experience, to construct it and then go out and use it and see if it works as it should. There are a few guidelines which should be followed: Always use the same brand of leader material. Always follow a published design if you do not have a pattern of your own. Make various types of leader for various conditions. One type is not suitable for all conditions. Be certain that all knots are firm and secure, test each one by tugging. Always ensure that any knot or line twist is untangled immediately.
As the butt section is about two thirds the thickness of the line it is attached to, a different leader is required for each line size. It is therefore necessary that the intermediate sections of the leader should vary in size. If the tapering of the leader is too great, there is every likelihood of the leader parting under the strain of a hooked fish.