What is leader material
A leader is a link made deliberately unlike the main line. Weaker or stronger, depending on what you fear on this water: the snag or the teeth. Both answers are correct, and they are opposites.
Why a separate link at all
A leader solves three different problems, and works differently in each: saving the rig on a snag, surviving a predator’s teeth and staying invisible to a wary fish. One link does not cover all three at once, which is why several leader materials exist.
When the leader is weaker than the main line
In float and feeder fishing the leader is set thinner than the main line. The logic is simple: on a snag it is the leader that parts, and you lose a hook rather than the whole rig with the feeder on it.
The gap is kept small, so that the weak link is a predictable one. Make the leader too fine and it will break on fish rather than on snags, and the point is lost.
When the leader is stronger
Pike fishing reverses this. Teeth cut through nylon and braid alike, so between the lure and the main line goes a link that is harder to bite through: a steel trace, a titanium one, or heavy fluorocarbon.
The same approach works where the bottom cuts: mussel beds, rock, concrete. Here the leader protects against the ground rather than the fish.
What they are made of
Steel holds teeth best and shows up most in the water. Titanium costs more but does not kink and returns to shape. Fluorocarbon is inconspicuous and abrasion-resistant, but will not stop pike teeth — it goes on for zander, perch and wary silver fish. Nylon as a leader stays where a weak link is the point.
Length and attachment
Length follows the job: for pike a short trace is enough, while for wary fish in clear water the leader is made longer so the main line sits further from the hook. Links are tied with a knot or joined with a snap — the snap is quicker, the knot is neater.
Hook size and shape is a separate subject, covered in the hooks section.
What we do not write here
We give no tables of which steel for which pike: the breaking strain of a trace is what the maker states, and it varies between neighbouring batches. Nor do we suggest fitting steel everywhere as insurance — where there are no teeth it only spoils the action of the lure.