Use a small, neat tube or nail knot to attach the smaller backing line to the larger fly-line end.

Either end of a level or double-taper fly line can be attached to the backing, but be absolutely sure you attach only the back end of a weight-forward fly line to the backing. Most weight-forward fly lines have a small tab on the back end stating "this end to reel." If your weight-forward line does not have such a tag, tie the backing to the long, small-diameter end which is the back end of this type of taper.

Once the knot is tied to the fly line back end (known as the running line), overcoat this junction with a coat or two of flexible, fast-drying, waterproof cement for an even smoother more durable junction. Allow the cement to dry before winding the fly line onto the reel.

Winding Fly Line Onto the Reel
Repeat the same procedure as used to wind the backing onto the spool to put the fly line onto the fly reel. If there is not enough room for the complete fly line, you must remove the fly line, cut the fly-line-to-backing junction and remove enough backing from the spool to allow the full line to fit onto the reel. If you have a weight-forward line, you may remove a section of the fly line's back end if the needed space adjustment is not too large (10 to 20 feet).

Leader-to-Line Connection
The needle knot is the best way to join the leader butt and fly line tip with a small, smooth connection. Next best would be to use the tube or nail knot. Either knot, when tied and trimmed neatly and overcoated with cement, functions beautifully.