Before wire can be bent into the shape of a hook it must be annealed (softened) through heating and slow cooling. Once a hook is formed it has to be re-tempered (hardened) again through heating and rapid and controlled cooling. The ideal hook is not so hard as to become brittle and not so soft as to open up and straighten under pressure from a big fish.

Gape and Shape

In theory a standard hook gape is equal to half its length, minus the eye. The gape of the hook has an effect on its hooking ability and generally, within limits, the bigger the gape the better the hook will perform. Bulky material applied to the shank of the dressed hook will decrease the gape and its ability to successfully hook a fish

The shape (or bend) of a hook also affects its hooking ability as does the point and the construction of the barb

Up Eyes or Down Eyes

Traditionally dry flies were tied on up-eyed hooks and wet flies on down-eyed. However, all salmon flies are tied on up-eyed hooks and are fished sub surface. Dry flies with up-eyes look good to the fly-tier but it is doubtful if it makes any difference to the fish

Barbed or Barbless

Most hooks are sharpened chemically and are available with or without a barb. Barbless hooks make it much easier to release both the fish and the angler’s fingers!

Barbed hooks can be made semi-barbless by crushing the barb down with a small pair of pliers. This tends to leave a bump that probably helps to prevent loss of the fish. Crushing the barb sometimes results in the barb snapping off and if not done with care can also snap the point of the hook

There is nothing so frustrating as spending time tying a really good fly and then snapping the hook point off whilst crushing the barb; so always crush the barb down before tying on the materials

The Long and the Short of Hooks

Hook sizes are given numbers. Perversely, the higher the number, the shorter the hook. For trout hooks the usual sizes are 8, 10, 12, 14, 16, 18 and 20. The in-between numbers 9, 11,13,15 etc are rarely used. Most standard size hooks from different manufacturers are similar in size but there is no absolutely agreed measurement of length for a particular hook number. This can pose problems when the rules of a fishing club dictate that only hooks of a certain maximum size may be used

Difficulty of hook sizing is particularly apparent with specially shaped hooks, e.g Partridge Klinkhamer hooks seem to bear no relationship to standard lengths

Long shank and short shank hooks are described with an X number. For example a size 10 / 2X Long shank hook has a gape of a normal size 10 hook but the length of the shank is the same as a hook that is 2 sizes larger, i.e. a size 6 hook, (2X does not mean two times as long). This sort of hook would be ideal for a nymph

Heavy weight and Light weight hooks

The wire that hooks are made from is also of variable thickness and is described as fine wire, standard wire or heavy weight wire. Generally speaking dry flies are tied on fine wire hooks and wet flies are tied on heavy weight hooks for obvious reasons

Standard dry fly hooks would be 1X fine wire so it will not sink so easily. Standard nymph hooks would be 2X long 2X stout. Long to represent the insect and heavy to make it sink. Wet fly hooks are made with 2X heavy wire to make them sink

Given all these variables there are literally hundreds of different kinds of hooks