Here is a frequently asked question about loop knots:

What is the best way to connect the leader to the fly line? And are loop knots worthwhile?

Q What is the best way to connect the leader to the fly line? And are loop knots worthwhile?

Connecting the leader to the fly line seems to be a personal thing with many experienced fly-fishermen. The standard nail knot is probably used most often, but it has the disadvantage of being a permanent connection, not allowing quick leader changes. Commercial slip-on braided leaders have come on the market of late, which have received mixed results. Some top fly-fishermen make their own loop knot from 50-braided line and claim good success.

Since the late 1960s, I have used the whipped loop knot, made with size A tying thread and a bobbin. Instructions can be found in the book Practical Fishing Knots. With a little practice, this knot can be installed in both ends of the line in minutes, and it will be stronger than the line - I have never had it fail. Also, the whipped loop tapers smoothly to the line, so it can't catch on the guides. Making the loop with two nail knots to hold it in place, as many prefer, requires the tier to take extra care to ensure a smooth connection that won't catch.