The snell is different from every other terminal knot: instead of tying to the eye, it wraps the line around the hook shank. That puts the pull directly in line with the hook, which improves the way it sets, a real advantage with bait and, especially, with circle hooks.
When and why to use it
Snell a hook for bait fishing, chunking, bottom rigs and any presentation using a circle hook, where the inline pull helps the hook rotate into the corner of the jaw exactly as it is designed to. It is a natural fit for bait fishing and building high-low rigs, and it lets you add a second snelled hook or a dropper cleanly.
How it works
You pass the line through the eye, form a loop back along the shank, then wrap the tag around both the shank and the loop several times before pulling the standing line to tighten the coils down the shank. On an up-eye or straight-eye bait hook it produces a clean, strong, inline connection.