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Diagram

Surgeon’s Loop

Double surgeon’s loop

A fixed loop tied quickly in the end of a line, for a loop-to-loop connection or to let a lure or fly move freely on the loop.

Loop · Beginner · Monofilament / Fluorocarbon · 5 steps

ApplicationsHow to tie it
Surgeon’s Loop, finishedSurgeon’s Loop, finished

Finished structure

Drawn from a rope model of this knot: which strand passes over which comes from where the rope actually lies.

  1. Double the line into a long bight and choose the finished loop sizeThe end of the line is doubled into a long bight, with the two parts side by side and a broad closed end forming the future loop.
    Move 1 of 1Double the line into a long bight and choose the finished loop sizeYou should now see: A long bight with both parts lying side by side and enough length to tie the knot without stealing the loop.

    Step 01

    Fold the end of the line back on itself to make a bight a little longer than the loop you want.

    You should now see

    A doubled section of line with the bight at one end and the tag lying beside the standing line.

    If it goes wrong

    Making the bight too short. You find out in step 2, when there is not enough doubled line to tie the overhand and still leave a usable loop.

    Fix: Unfold it and double more line. The spare tag is trimmed off at the end.

    Why: The doubled line is tied as if it were a single strand, so both the knot and the loop come out of this length.

  2. Tie a loose overhand in the doubled line, keeping the bight openThe doubled line is bent into a loose overhand knot while the long bight remains open beyond it.
    Move 1 of 3Tie a loose overhand in the doubled line, keeping the bight open
    Pass the entire bight through the overhand onceThe doubled bight has passed through the loose overhand once; this is only the first of the two required passes.
    Move 2 of 3Pass the entire bight through the overhand once
    Take the whole bight through the opening a second timeThe bight has now passed through the overhand twice, forming the loose double-overhand core of the Surgeon's Loop.
    Move 3 of 3Take the whole bight through the opening a second timeYou should now see: Two complete passes of the doubled line lie in the overhand; a single pass is not the finished knot.

    Step 02

    Tie an overhand knot in the doubled line, then pass the bight through the same overhand a second time.

    You should now see

    A loose knot showing two turns of doubled line around each other, the bight sticking out one side and the standing line and tag out the other.

    If it goes wrong

    Making only one pass, or letting the two strands of the double twist over each other. You see a single crossing, or strands that swap sides inside the knot.

    Fix: Back the bight out, lay the two strands flat side by side, and make both passes again.

    Why: Two passes make it a surgeon's loop, a double overhand tied in doubled line. Animated Knots notes that a third pass adds little and makes the knot bulkier.

  3. Set the loop size, moisten the knot, and pull both line ends evenlyThe seated Surgeon's Loop has a compact two-pass double-overhand at its base and a stable fixed eye beyond it.
    Move 1 of 2Set the loop size, moisten the knot, and pull both line ends evenlyYou should now see: A compact double overhand grips the doubled line, the two parts lie side by side, and the loop keeps the size you set.
    Inspect the two passes and trim the tag only after a firm test pullThe finished Surgeon's Loop is loaded for inspection: two overhand passes remain compact and the fixed loop stays the same size.
    Move 2 of 2Inspect the two passes and trim the tag only after a firm test pullYou should now see: Two passes remain visible, the knot is symmetrical and closed, and the fixed loop does not change size under load.

    Step 03

    Slide the knot along the doubled line until the loop is the size you want.

    You should now see

    A loop of the size you need, with the loose knot sitting where you want it on the doubled line.

    If it goes wrong

    Leaving the loop size until after the knot starts to close. Once it tightens, the loop cannot be changed.

    Fix: If the knot has started to close on a loop of the wrong size, loosen it with a fingernail and slide it before it sets.

    Why: Loop size can only be changed while the knot is loose. Once it closes, the loop stays that size.

  4. Surgeon’s Loop — step 4 of 5Step 4 of 5. Wet; loop pulled against standing line and tag held together until it closes. This step is the line being placed now. Working is the end already placed. Standing is the line that stays. What is still to come is drawn lighter. A bight in the standing line, overhand through the bight, loop stays open under load.
    4
    step 04 · schematic

    Wet; loop pulled against standing line and tag held together until it closes.

    Step 04

    Wet the knot, then pull the loop against the standing line and tag held together until the knot closes.

    Wet; loop pulled against standing line and tag held together until it closes.

    You should now see

    A tight, rounded knot with the loop on one side, the standing line and tag on the other, and no turns sitting loose.

    If it goes wrong

    Pulling only the standing line so the tag side stays loose. The knot looks lumpy and closes unevenly.

    Fix: Wet the knot again and pull the loop against the standing line and tag together.

    Why: Animated Knots says to lubricate and pull tight without naming which parts to pull; pulling the loop against both strands of the double closes it evenly.

  5. Surgeon’s Loop — step 5 of 5Step 5 of 5. Tag trimmed close to the knot. This step is the line being placed now. Working is the end already placed. Standing is the line that stays. What is still to come is drawn lighter. A bight in the standing line, overhand through the bight, loop stays open under load.
    5
    step 05 · schematic

    Tag trimmed close to the knot.

    Step 05

    Trim the tag close to the knot.

    Tag trimmed close to the knot.

    You should now see

    A short tag end and a closed knot that does not move when you pull on the loop.

    If it goes wrong

    Trimming before the knot is fully closed. The tag can pull back inside the knot.

    Fix: If the tag is already cut and the knot is loose, cut the loop off and tie it again.

    Why: Trim last, after the knot has closed under a firm pull.

HTH · Reference layout

Surgeon’s Loop — finished-state checks, on the shared reference layout

Surgeon’s Loop — finished-state checks, on the shared reference layout
Hook the Horizon reference plate
Failure modes

When this family fails, it fails as these. The recovered end still outranks the name.

Fixed-loop family

A loop that stays the size you made, with a return that cannot cinch.

  • !Loop cinched around the hardware — action is dead
  • !Return path reversed, so it becomes a slip loop
  • !Fluoro in a lock that only behaves on mono
Fails when
  • !Seated on the standing line alone, leaving the tag side loose so the tag pulls back inside
  • !Tag trimmed before the knot fully closed, leaving it loose
  • !Strands of the double crossed over each other inside the knot
  • !Loop changes size under a test pull, showing the knot has not seated
Geometry

  • Single pass only — not a Surgeon's loop

    May slip and the eye walks

    Double pass is the minimum; one pass is an overhand loop · step 02

  • Messy multi-pass body

    Weaker eye, bulk that ticks

    Clean passes keep the lump compact and load-bearing · step 02

  • Passes not completed through the loop

    Unreliable — the eye never locked

    Every pass must go through the loop before the seat · step 03

If you saw this

  • Too bulky for small guides or keepers

    Check

    • ?Compare to Perfection Loop size

    Then

    • →Use Perfection Loop
    • →Drop to double surgeon

  • Finished check failed — Single overhand only

    Check

    • ?Double overhand completed on the doubled line
    • ?Loop size stable after draw
    • ?Tags exit cleanly

    Then

    • →Retie. Incomplete double overhand fails as a fixed loop.

  • Single pass only — not a Surgeon's loop

    Check

    • ?May slip and the eye walks
    • ?Inspect step 02

    Then

    • →Retie. Do not dress a defective structure and call it seated.

  • Messy multi-pass body

    Check

    • ?Weaker eye, bulk that ticks
    • ?Inspect step 02

    Then

    • →Retie. Do not dress a defective structure and call it seated.

  • Passes not completed through the loop

    Check

    • ?Unreliable — the eye never locked
    • ?Inspect step 03

    Then

    • →Retie. Do not dress a defective structure and call it seated.
Same family

Same failure class, different geometry. Open the plates — Diagnose still starts from the symptom.

This failed — start Diagnose

Why this knot

What it earns its place with, what it costs, and what to reach for instead.

Best for
Loop connectionsQuick to tie
Not ideal for
  • When the absolute smallest loop knot is required
  • Very fine tippet where the double-overhand bulk matters
Common mistakes
  • Doubling too little line to tie the overhand and still leave a usable loop
  • Making only one pass through the overhand
  • Letting the two strands of the double twist over each other inside the knot
  • Trimming the tag before the knot closes, or pulling only the standing line
Alternatives
  • Perfection LoopBeginner

    A small fixed loop in the end of a leader, tippet or fly line that lies in line with the standing line

  • Dropper LoopIntermediate

    A fixed loop that stands out from the middle of a line or leader, as an attachment point for an extra fly or hook

  • Bimini TwistAdvanced

    Making a double line with a loop at the end, for loop-to-loop leader connections or as the doubled line in knots such as the Yucatan

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