Nail knot
Knot · Last reviewed 2026-08-19
The join between a fly line's plastic coating and a nylon leader or backing — two materials that will not knot to each other. It works by wrapping rather than by knotting, and it is why a fly line has ends at all.
A FLY LINE IS NOT LINE IN THE SENSE THE REST OF THIS CATALOGUE MEANS. It is a braided or monofilament core inside a thick plastic coating, and the coating is what gives it the weight that makes fly casting possible. Nothing about it will knot to nylon: it is far too thick, it is compressible, and a conventional knot tied in it simply crushes the coating.
THE NAIL KNOT SOLVES THIS BY NOT KNOTTING THE FLY LINE AT ALL. The nylon is wrapped in a tight coil around the outside of the fly line and its tag is threaded back under its own wraps. When it is drawn up, the coil bites into the coating and grips along its whole length. The fly line is passive throughout — it is wrapped, not tied — and that is the entire trick.
THE NAME IS THE TOOL. A nail, or more usually a fine tube or a purpose-made tool, is laid alongside the fly line to hold a channel open while the wraps are made, so the tag can be passed back under them. Removing the tube leaves the tag threaded through. Without something to hold that channel, the knot is close to untieable.
IT IS USED AT BOTH ENDS OF THE FLY LINE AND FOR DIFFERENT REASONS. At the front it joins the leader butt, and the join must be smooth enough to pass through the tip ring when a fish runs and the leader knot comes inside the rod. At the back it joins the backing, where the requirement is simply that it holds and is small enough to lie flat on the spool under everything wound on top of it.
WHAT IT COMPETES WITH IS A WELDED OR MANUFACTURED LOOP. Most modern fly lines arrive with loops already fitted at both ends, and `loop-to-loop-connection` is then the quick, field-repairable answer — which is why many anglers never tie this knot. Two things keep it worth knowing: a factory loop that has failed leaves a fly line with a bare end in the middle of a session, and a nail knot is markedly smoother through the rings than any loop-to-loop, which matters when a fish is taking line and the join is travelling.
AND A COATING THAT HAS BEEN CRUSHED DOES NOT RECOVER. Over-tightening does not make this knot stronger; it drives the coil through the coating onto the core, and the line then hinges and eventually parts there.
- Used for
- Joining two lines
- Holds in
- Monofilament, Fluorocarbon, Fly line, Backing
- Do not use in
- Braid, Wire
How to tie it
These written steps are the instruction. The diagram supports them.
- Lay the end of the fly line, the end of the nylon, and a fine tube or nail alongside each other, all pointing the same way and overlapping by about 8 cm.
- Wrap the nylon tag in tight touching turns around all three — fly line, tube and its own standing part — working back towards the end of the fly line. Six or seven turns.
- Pass the nylon tag back through the tube, so that it runs underneath all the wraps just made.
- Withdraw the tube carefully, leaving the tag threaded under the coil.
- Wet the coil thoroughly.
- Draw it up by pulling both ends of the nylon a little at a time, alternately, so the coil closes evenly onto the fly line without bunching. Stop as soon as the turns are tight and touching.
- Trim both the nylon tag and the fly line tag flush, and check the join by drawing it through the tip ring by hand.
Finishing it properly
- Draw up alternately from both ends, a little at a time. A coil closed from one end bunches.
- Stop tightening when the turns are touching. There is no gain past that point and there is real damage.
- Trim both tags flush — this is the one connection where a proud tag is worse than a slipped one, because it catches in the tip ring.
- A flexible coating over the finished knot smooths the step from nylon to fly line and helps it through the rings. Use one made for the purpose, not a hard glue, which creates the hinge it is meant to prevent.
How it fails
The dominant failure is over-tightening, and it is invisible at the time. Drawn too hard, the coil cuts through the plastic coating onto the core; the join feels solid, then hinges at that point and parts there later, usually with a fish on. The tell is a fly line with a permanent sharp kink just behind the join. The second failure is a coil that has bunched rather than closed evenly, which grips over a shorter length than it should and slips progressively — the leader gets longer over a session. Inspect by flexing the join: it should bend in a smooth curve, never hinge at a point.
The welded loop, and what a failed one leaves you with
Most fly lines now arrive with loops moulded or welded at both ends, and most anglers therefore never tie this knot. That is a reasonable position right up to the moment a loop fails, which is when the difference between the two connections becomes concrete.
WHAT A FACTORY LOOP IS. The fly line's own end doubled back and bonded to itself inside a sleeve of coating. It is quick, it is strong enough, and `loop-to-loop-connection` can then change a whole leader in seconds with cold hands — which is genuinely valuable in fishing where leaders are swapped constantly.
HOW THEY FAIL, AND IT IS RARELY DRAMATIC. The bond creeps. The loop opens slightly, then further, and the coating at the base of it cracks. The usual sign is a loop that has gone slightly furry or that shows a pale line where it is separating, and it is worth looking at both loops at the start of a season rather than discovering it with a fish attached.
WHAT YOU HAVE WHEN IT GOES. A fly line with a bare, blunt, uncoated end and nothing to interlock with — on the bank, mid-session. A nail knot is the repair, and it needs a fine tube and about two minutes. An angler who has never tied one is finished for the day.
AND THE PERFORMANCE DIFFERENCE THAT ARGUES FOR IT EVEN WHEN NOTHING HAS FAILED. A loop-to-loop is a hinge and a lump. When a fish runs and the leader knot comes back inside the rod, that lump knocks through every ring — audibly, and with a small jolt transmitted to a hook hold that may be marginal. A nail knot is a smooth tapered step and it travels through the rings almost silently. On small fish this is invisible; on a fish that takes line repeatedly it is not.
THE SENSIBLE POSITION IS BOTH. Fish the factory loops, carry a length of leader butt and a tube, and know the knot. It is the classic case of a skill whose value is entirely in the session where you need it.
Practitioner consensus
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
- Still Water Fly-Fishing — Andre Deutsch, 1952 (Specialist angling publication)Relied on for: Stillwater fly practice: leader construction, teams of flies on droppers, and the joins between backing, fly line, leader and tippet.States this directlyCitation checked — the work exists and is described correctly
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: Long-running published description of British game angling practice, including leader and tippet construction and the fly-line connections it rests on.States this directlyCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated descriptions of established connection convention, recorded as practitioner consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly
Where to go next
Where it is used
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Fly fishing
An arrangement joined to the knot that actually builds it, written where the knot is characteristic of that arrangement rather than merely possible in it. This is the edge a reader travels: they arrive looking for the arrangement and need the connection it depends on.
- Still Water Fly-Fishing — Andre Deutsch, 1952 (Specialist angling publication)Relied on for: Stillwater fly practice: leader construction, teams of flies on droppers, and the joins between backing, fly line, leader and tippet.States this directlyCitation checked — the work exists and is described correctly
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: British game angling practice, including leader and tippet construction and the fly-line connections it rests on.States this directlyCitation checked — the work exists and is described correctly
What it joins
- Fly leaders and tippetWhere the leader butt meets the fly line. It competes with a factory welded loop, and the two reasons to know it are that a failed loop leaves a bare fly line mid-session and that a nail knot runs through the tip ring markedly more smoothly when a fish takes line.
- Fly linesThe join at both ends of a fly line, and the reason a fly line can be connected to anything at all. A fly line is a plastic coating over a core, far too thick to knot and crushable, so the nylon is wrapped around the outside of it and the fly line itself is never tied.
What these connections rest on (2)
Practitioner consensus — 2 connections
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Fly leaders and tippet
An arrangement joined to the knot that actually builds it, written where the knot is characteristic of that arrangement rather than merely possible in it. This is the edge a reader travels: they arrive looking for the arrangement and need the connection it depends on.
- Still Water Fly-Fishing — Andre Deutsch, 1952 (Specialist angling publication)Relied on for: Stillwater fly practice: leader construction, teams of flies on droppers, and the joins between backing, fly line, leader and tippet.States this directlyCitation checked — the work exists and is described correctly
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: British game angling practice, including leader and tippet construction and the fly-line connections it rests on.States this directlyCitation checked — the work exists and is described correctly
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice: reel filling, leader and dropper construction, and the connections each arrangement rests on.States this directlyCitation checked — the work exists and is described correctly
- Coarse Fishing — A. & C. Black, 1912 (Specialist angling publication)Relied on for: Classical coarse angling practice: hooklengths, loops, droppers and the terminal arrangements built from them.States this directlyCitation checked — the work exists and is described correctly
Fly lines
An arrangement joined to the knot that actually builds it, written where the knot is characteristic of that arrangement rather than merely possible in it. This is the edge a reader travels: they arrive looking for the arrangement and need the connection it depends on.
- Still Water Fly-Fishing — Andre Deutsch, 1952 (Specialist angling publication)Relied on for: Stillwater fly practice: leader construction, teams of flies on droppers, and the joins between backing, fly line, leader and tippet.States this directlyCitation checked — the work exists and is described correctly
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: British game angling practice, including leader and tippet construction and the fly-line connections it rests on.States this directlyCitation checked — the work exists and is described correctly
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice: reel filling, leader and dropper construction, and the connections each arrangement rests on.States this directlyCitation checked — the work exists and is described correctly
- Coarse Fishing — A. & C. Black, 1912 (Specialist angling publication)Relied on for: Classical coarse angling practice: hooklengths, loops, droppers and the terminal arrangements built from them.States this directlyCitation checked — the work exists and is described correctly
Worth understanding first
- Choosing a knot for the line you are usingA material problem in the purest form the record describes: the fly line's coating does not deform and grip the way nylon does, it crushes. The solution is not a different knot in the fly line but no knot in the fly line at all.
- Joining two lines: what the join has to surviveThe case that record's three requirements do not quite cover, because one of the two lines is not line. Its requirement that a join be smooth enough to pass through the rings is the deciding one here, and it is why this knot survives alongside the loop that mostly replaced it.
What these connections rest on (2)
Practitioner consensus — 2 connections
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Choosing a knot for the line you are using
A knot joined to the explainer that sets out the principle it is an instance of. The explainers were written first and each names families of solution; these edges are what let a reader move from the principle to a knot that embodies it.
- How to Tie Fishing Knots — uni, blood, improved blood, surgeon's and loop knots — Recreational Boating & Fishing Foundation (Take Me Fishing) (Angling or fisheries organisation)Relied on for: The double surgeon's knot sequence, and the grouping of knots by the connection each is for.States this directlyPassage read and verified
- Fishing Knots — which knot for which line — Vermont Fish & Wildlife Department (Government fisheries body)Relied on for: A state wildlife agency grouping knots by job and stating that the surgeon's knot joins lines regardless of diameter or line type.States this directlyPassage read and verified
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice: reel filling, leader and dropper construction, and the connections each arrangement rests on.States this directlyCitation checked — the work exists and is described correctly
- Coarse Fishing — A. & C. Black, 1912 (Specialist angling publication)Relied on for: Classical coarse angling practice: hooklengths, loops, droppers and the terminal arrangements built from them.States this directlyCitation checked — the work exists and is described correctly
Joining two lines: what the join has to survive
A knot joined to the explainer that sets out the principle it is an instance of. The explainers were written first and each names families of solution; these edges are what let a reader move from the principle to a knot that embodies it.
- How to Tie Fishing Knots — uni, blood, improved blood, surgeon's and loop knots — Recreational Boating & Fishing Foundation (Take Me Fishing) (Angling or fisheries organisation)Relied on for: The double surgeon's knot sequence, and the grouping of knots by the connection each is for.States this directlyPassage read and verified
- Fishing Knots — which knot for which line — Vermont Fish & Wildlife Department (Government fisheries body)Relied on for: A state wildlife agency grouping knots by job and stating that the surgeon's knot joins lines regardless of diameter or line type.States this directlyPassage read and verified
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice: reel filling, leader and dropper construction, and the connections each arrangement rests on.States this directlyCitation checked — the work exists and is described correctly
- Coarse Fishing — A. & C. Black, 1912 (Specialist angling publication)Relied on for: Classical coarse angling practice: hooklengths, loops, droppers and the terminal arrangements built from them.States this directlyCitation checked — the work exists and is described correctly
Instead of this
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Loop-to-loop connection
Fly literature treats these as the two answers to the same connection and separates them on profile and field-repairability, which is what the choice actually turns on.
- Still Water Fly-Fishing — Andre Deutsch, 1952 (Specialist angling publication)Relied on for: Stillwater fly practice: leader construction, teams of flies on droppers, and the joins between backing, fly line, leader and tippet.States this directlyCitation checked — the work exists and is described correctly
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: British game angling practice, including leader and tippet construction and the fly-line connections it rests on.States this directlyCitation checked — the work exists and is described correctly
History and culture
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Nylon, and what synthetic line changed
A knot joined to the material transition that produced or transformed it. Written where the knot is genuinely an artefact of synthetic line rather than merely contemporary with it, which is why the wire termination in this file does not carry it.
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice: reel filling, leader and dropper construction, and the connections each arrangement rests on.States this directlyCitation checked — the work exists and is described correctly
- Coarse Fishing — A. & C. Black, 1912 (Specialist angling publication)Relied on for: Classical coarse angling practice: hooklengths, loops, droppers and the terminal arrangements built from them.States this directlyCitation checked — the work exists and is described correctly
- Sea Angler — Bauer Media (Specialist angling publication)Relied on for: British sea angling practice: shock leaders, multi-hook trace construction and the dropper loops a trace is built from.FishingHQ's interpretation of what it saysCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated descriptions of established connection convention, recorded as practitioner consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly
Sources for this page
- Still Water Fly-Fishing — Andre Deutsch, 1952 (Specialist angling publication)Relied on for: Stillwater fly practice: leader construction, teams of flies on droppers, and the joins between backing, fly line, leader and tippet.States this directlyCitation checked — the work exists and is described correctly
- Trout & Salmon — Bauer Media (Specialist angling publication)Relied on for: Long-running published description of British game angling practice, including leader and tippet construction and the fly-line connections it rests on.States this directlyCitation checked — the work exists and is described correctly
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice: filling a reel, leader and dropper construction, and the connections each arrangement is made with.States this directlyCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated descriptions of established connection convention, recorded as practitioner consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly
How FishingHQ labels evidence is explained in the evidence policy.