The PR knot does the same job as the FG knot, joining braid to a leader in a thin, super-strong connection, but it gets there a different way: the braid is tightly wound onto the leader with a bobbin tool under tension. The result is a slim, bombproof splice that big-game and offshore anglers rely on for heavy leaders.
When and why to use it
Use the PR knot when you want maximum reliability joining braid to a heavy leader for tuna and other big game, and you do not mind carrying a bobbin. Many anglers find it more consistent than the FG on heavy leaders, at the cost of needing the tool. For lighter inshore leaders, the FG or a double uni is quicker.
How it works
Using a PR bobbin loaded with braid (or thread), you hold the leader under tension and let the weighted bobbin wrap the braid tightly up and back down the leader, then lock it off with half hitches and, often, a light coat of glue. The tight, even wraps bite into the leader for a slim, extremely strong connection.
Tip Learn it at home with the bobbin, and keep tension on the leader throughout. The PR knot lives or dies on tight, even wraps, which is exactly what the bobbin gives you, but only if the leader stays taut while you wind. Animated Knots does not cover it, so find a good video and practice.