Furled leaders may remain a mystery to you until either you see someone make one or buy the video from KS for $15.00. [I am a satisfied customer].
Here's an analogy. Take a piece of thread or yarn, twine etc. Twist it tightly and then loosen your hold and let it twist around itsel. [I make extended bodies for flies like this all the time]
Now with a furled leader you are twisting a bunch of interconnected loops and performing a similar process. Is it as clear as mud?
BTW Fly Fishing-Tying CAN be expensive but it doesn't have to be. Kind of like golf You can buy a used driver for three bucks at a tag sale or spend six hundred for the latest high-tech driver.
One of my favorite fly fishing books is "The Colonial Angler" It allows you to step back in time and see that there are many ways to fly fish and that what is advertised today is today's style of fishing, not the only way to enjoy fly fishing.
Ed
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my humble low budget fishing site
" Fishermen, hunters, wood choppers, and others,
spending their lives in the fields and woods,
in a peculiar sense a part of Nature themselves,
are often in a more favorable mood for observing her,
in the intervals of their pursuits,
than philosophers or poets even,
who approach her with expectation."
Henry David Thoreau