How to Tie the Span Loop

How to Tie the Span Loop

Usage

The Span Loop makes a compact, non-jamming loop in the middle of a line without needing either end. Ashley used it for hooking a tackle block onto a rigging span, and it does the same job today as the loop in a Trucker’s Hitch, a tarp ridge attachment point, or a camp gear hang. Compared with other mid-line knots like the Alpine Butterfly or Double Dragon Loop it is simpler to tie, but it is less capable under heavy multi-directional load and it needs to be set carefully before you tension it.

Keep it out of life-safety work. For a mid-line loop that has to hold a person, tie the Alpine Butterfly. You can see how the Span Loop forms in the Knot IQ app.

Why Learn the Span Loop?

The Span Loop is one extra tuck past the mid-line Slip Knot, and that tuck is the whole point: the Slip Knot binds brutally tight under tension, especially on paracord, while the Span Loop releases by hand. Whenever you would tie a mid-line Slip Knot for camp or utility work, this is the upgrade.

Common Uses

• Rigging & Sailing:
  • Hooking a tackle block onto a span that is made fast at both ends and hauled at the centre — Ashley’s own worked example for #1049.
• Camp & Tarp:
  • Mid-line attachment point on a ridgeline for a tarp, a stake line or a gear hang.
  • The loop element in a Trucker’s Hitch, where it has to come undone afterwards.
• General Utility:
  • A drop-in replacement for the mid-line Slip Knot anywhere that knot would jam.

Not for climbing, arborist or rescue anchors. That use appeared in our own earlier copy and nothing outside it supports the claim — see Security Level below.

ABOK Number (Ashley Book of Knots) #1049 Other Names None listed Category Mid-Line Knots

Notable Features

• Holds Its Shape: Stays put under a steady pull once it is properly set.
• Quick to Tie: Forms faster than the Double Dragon Loop, great for urgent setups.
• Non-Jamming: Easy to untie after heavy loads, unlike some knots.
• No Ends Needed: Ties anywhere along a line that is already rigged.

Variations

No true variations of the Span Loop are documented. No source in our collection prescribes a backup knot for it either — the documented caution is about setting the knot correctly, not about backing up a finished one.

Similar Knots

Alpine Butterfly Loop vs. Span Loop

• Pros: The Alpine Butterfly Loop takes multi-directional load and is the mid-line loop actually used in climbing — the one to reach for when the load is a person.
• Cons: Slightly more complex to tie than the Span Loop.

Double Dragon Loop (Mid Line) vs. Span Loop

• Pros: The Double Dragon Loop (Mid Line) is more secure under heavy load and less likely to jam — though it too is a utility knot with no life-safety endorsement.
• Cons: Harder to tie and less intuitive for quick setups.

History

The Span Loop comes out of the maritime rigging tradition, where a mid-line loop was needed to hook a tackle block onto a span. Clifford Ashley records it as #1049 in The Ashley Book of Knots and calls it one of the strongest and most secure of its series. Its modern life is camp and utility work — tarp lines, gear hangs and the loop in a Trucker’s Hitch — rather than technical rope work.

Security Level

Set correctly, the Span Loop is a secure mid-line loop and unties by hand afterwards. Ashley rated it highly, but that is a judgement from 1944, not a measurement. Its own documented weakness is set-up, not shock — it can collapse into a deformed shape if it is pulled before it is properly set.

Ashley adds one caution worth repeating: do not stretch the rope drum-taut before loading, because a direct sideways pull is more than any tight-stretched rope can take. On anchors, the evidence runs against our older copy — a professional arborist and DJ both name the Alpine Butterfly for high-risk work. Use the Span Loop for camp and utility loops; use a knot rated for life load when a person is on the line.

Downsides

• Tightening required: May slip if not properly tensioned during tying.
• Limited versatility: Less effective for multi-directional loads compared to the Alpine Butterfly.
• No test record: Nothing published measures its strength or security, and no standard names it.

Structure

1. Select a point on the rope and form a small loop by twisting the rope once, creating a single twist.
2. Bring the loop over the standing line to form a larger loop, keeping the twist intact.
3. Pass the larger loop under the standing line and through the small twisted loop.
4. Pull the standing line and the loop to tighten, ensuring the knot forms a secure mid-line loop.
5. Check the knot for symmetry and test under light load to confirm it holds.

Pro Tip: Ensure the initial twist is tight to prevent slippage during tightening.

Set it before you load it. Pulled or loaded before it is dressed and snugged, the Span Loop can collapse into a deformed shape that is not the knot you meant to tie. And do not tension the line drum-tight first — Ashley’s warning is that a direct sideways pull is too much for any tight-stretched rope.

FAQ

Is the Span Loop strong enough for heavy climbing loads?

No. Do not use it for climbing anchors — tie the Alpine Butterfly instead.

What’s the best rope for the Span Loop?

Strong, smooth ropes like nylon or polyester hold the shape best. Avoid stiff or worn line, which resists dressing and makes a sloppy loop.

How does the Span Loop compare to the Alpine Butterfly Loop?

The Span Loop is simpler to tie, but the Alpine Butterfly is stronger for multi-directional loads.

Can the Span Loop be used in rescue operations?

No. Nothing in the rescue literature we searched names this knot, and it has no test record behind it. Rescue loads belong on knots that are rated and taught for the job.

Why choose the Span Loop over the Double Dragon Loop?

The Span Loop is faster and easier to tie, making it better for quick mid-line loops.

Important Notes on Safety

Common failure points are loose tightening and improper loop formation, either of which lets the knot slip or collapse. Always verify the knot is snug and test it under light load before you rely on it — and keep it off climbing, arborist and rescue anchors entirely.

Check rope for wear or slickness before tying.

Ensure the twist and loop are symmetrical for a secure hold.

Practice tying in low-stakes settings first.