I'm not talking about a 'how to' manual. I look at a whole wall of plugs that are different shapes and colors and think what are these intended for.
Something that would tell me or group them into; Deep running, middle level, sinking, floating, imitation of what?, intended for what, etc.
They all must have a sweet spot or design target of operation. From that point of depth, speed or motion a fisherman could add variations and changes in tecnique to suit local conditions and styles.
Sorry, just a minor rant. ;D