The Contented Angler
"The Genuine Fly Shop"
The Contented Angler
147 Jefferson Avenue
Lower Burrell, Pa.  15068
724-337-0437
EMAIL
scud hook
dre fly hook
fig. 1  standard dry fly hook.
All of this terminology for one little hook.  How is a new tyer expected to understand
it all?  Let's take a look at the reasoning behind all of this.
The green lines in fig. 1 represent what is meant by shank length
The blue line represents gape width (pronounced gap).
Notice how the down eye reduces the gap width.  If you build up the body too much,  
this also reduces gap width.  See fig. 5.
The larger the gape the more chance you have of initially hooking the fish.
Shank length is normally twice the gape width so if you have a 4mm gape,  you will
have an 8mm shank length.
Notice in fig. 2  how the upturned eye opens the preferred angle but
you may have to compromise and go with a wider gape on a small
hook.

Great! then why don't all hooks have a large gape?
Because a large gape increases the angle of pull and the more angle
you have,  the more chance you have of losing the fish throughout
the struggle.  You want a nice straight pull.
Therefore,  we have to compromise between gape width and shank
length.
fig. 2 upturned eye hook.
streamer hook
fig. 3 6XL Limerick bend streamer
hook.  Imagine pushing the
bottom of the hook up and to the
rear. The Limerick hook places the
point more to the rear of the hook.
fig. 3 A size 6,  6XL streamer hook has a size 6 gape with a shank
length that is equal to a hook 6 sizes larger.  Notice the nice straight
pull. A limerick bend streamer hook pushes the bend more to the
rear of the hook which helps in hooking short strikers.  The Limerick
hook has a very acute bend on the bottom of the bend.
egg hook
fig. 4 XS egg hook
You will often see XS or extra short shank hooks labeled as egg
hooks. A size 10 5XS hook has the gape of a size 10 hook and a
shank length of a hook that is 5 sizes smaller.
egg hook
fig. 5
egg fly is completed.  This is the main reason for X-short hooks.  
We shorten the shank length and still maintain the gape width.   
The blue line represents our new gape width.
Understanding hook terminology
for the new fly tyer
We now come to the popular scud hook, fig. 6 or continuous bend
hook. The scud hook has very little gape but a nice straight pull.  
There is really no shank to speak of.  A nice hook to create realism
but it has to be more difficult to initially grab some flesh with the
small gap.
Share
The ideal hook should have a slightly turned down eye that is
completely closed,  a small barb,  a short distance between point
and barb and the hook should be tempered properly.
A properly tempered hook should bend and then break before it
opens up.
The confusion comes in when a Green Drake pattern calls for a
size 10 dry fly hook.  Use a size 10 standard hook and your fly will
be too small!  This usually happens when the author doesn't
know which hook to use,  and it happens frequently.
curved hook
fig. 6
bend hook