Picture of a typical fly line box.

WF-5-S is the common format for fly line description on the packaging. Each of the three parts of the code tell the angler something different.

WF: This first component indicates the taper style. There are only two that as a beginner we need to think about; WF (weight forward) and DT (double taper). WF fly line is designed with extra weight - you guessed it - at the head of the line. This helps when casting against the wind and/or to get some extra distance. If you purchase this type of line, make *sure* that the proper end is attached to the backing (reel side) so that the weight is actually at the forward end.

DT: Double taper is line that has a narrower diameter at the head and the tail (15 ft), so that you get <---narrow 15ft------thicker 60ft------narrow 15ft---> clear as mud?

L and ST: Level and Shooting Taper are less common and more often used by experienced fly fishers. I have been encouraged to ignore these for the first few years, so I am.

5: The second component of the code indicates the weight. This number should be matched to your rod/reel weight number as a beginner. Many, many fly fishing articles discuss the benefits of using a weight (or two) smaller than your rig, but that is another advanced technique, and for now just make it match. For the sake of knowledge; the number is the weight in grains of the first 30ft of fly line.

S: The last component is an indication of whether the line is Sinking or Floating line. S or F. Floating line is the most versatile as split-shot weights can always be added to help get a streamer or nymph down the water column. Sinking line sinks... there really isn't any middle ground. I have two reels, one with each type of line.

S/F and I: Sinking/Floating is line that floats, except at the tip. Also called Sinking Tip line. A sort-of floating, sort-of sinking line is Intermediate or I.

So, when you see DT-7-F; that's Double Tapered, 7 weight, Floating line. Just to repeat what I have been told, use WF or DT, match the line weight to the rod/reel and start with floating line if you only have one rig.

Color

The general rule of thumb is; if it sinks, match the water color or darker. If it floats, pick a color that you can easily see, because the fish will see it no matter the color.