Trajan Weaver send me an email and noted, There is a scene (the final shot of an older man fishing, tying a fly on the end of his line) in “A River Runs Through It.” Would you show me, step by step, how he was tying on the fly? I would much appreciate it.
The knot is the Turle. It was widely used with gut leaders, and was designed so that the tippet came straight out of the eye, while the knot itself was tied around the head of the fly. It’s just a slip knot. The tippet is threaded through the eye, and then the slip knot tied. The fly is placed through the slip knot, and it’s drawn tight over the head of the fly. The Double Turle is a modification of the original Turle in which the end of the leader goes through the knot twice. See Below.
Here’s an illustration from MeClane’s New Standard Fishing Encyclopedia (1974, Holt, Rinehart, Winston, NY.)