Updated: Sep 17, 2022
Fly fishing is confusing enough but then you need to worry about line weights and rod weights . DT, WF, 4x leaders, 6x tippet, what does this all mean and how do is all work together? This is a very common question and easy for beginners to confuse.
The basic thing to understand is that the rod goes with the line weight. That is one system separate from the leader and tippet. Of course they are all connected to work together, but if you think of them as two independent tools, then it is easier to match up.
Whatever the rod weight is, the line weight needs to be as well. Five weight rod means five weight line, regardless of the taper. There are specialized lines for species, different colors, and performance claims, all extra that you don't need to take into account for a basic setup. The letters on the box refers to the taper; WF means weight forward, DT means double tapered. WF means the front 30' of your 90' fly line is thicker than the rest. This helps cast longer distances and turn over larger flies. DT means that the thickest part of the fly line is the middle 30'. You don't get the help casting, but the line lands a little more quietly on the water. Do not get a heavier weight, or higher numbered, line as this will overload your rod and can potentially break it.
Attached to your fly line is your leader, which is tapered as well. The thinnest end where you attach your fly is your tippet. Just like the rod and line works together, so should your leader and fly. We have a rule of three in regards to this: fly size divided by 3 will give you your leader size. For example, size 18 hook divided by 3 you would want to use a 6x leader, size 12 hook, 4x tippet. You can usually go a size up or down either way for flexibility, but usually if you can get away with the smaller tippet, go for it.
My set ups for fly fishing in the Shenandoah Valley of Virginia are:
-3 weights that are 7'6" for brooke trout (12" fish or smaller)
-5 weights that are 8'6" for larger trout (12'-20"+)
-8 weights for smallmouth and largemouth bass (very big flies)
A nice balanced rod and line makes your cast smoother and the whole system just work better. Don't let the numbers go to your head, just match them up and head out to the stream.