Do a "fly swaps" search on the search thingy. To answer your question, read this: [url=][/url:b7cf7]
That should get you up to speed.
To the GP and LF, suggestion to incorporate this in some sort of Fly fishing Basics or Fly tying basics section on FAOL. This question comes up about twice a year.(I know, it prolly is somewhere but I can't find it.)