Slack Anchors
Slack anchor systems are commonly used in rope access, though they appear in other rescue environments as well. Their appeal lies in simplicity—and in many rope access situations, where dynamic loading or sudden failure is rare, slack anchors are entirely appropriate.
However, simplicity doesn’t mean simplicity of thought. These anchors require purposeful alignment, clear role separation, and full load-bearing capability from all components.
What Is a Slack Anchor?
A slack anchor system is built with two or more anchor points, but only the primary anchor is tensioned. The secondary anchor remains unloaded—held in reserve as a backup.
Key traits:
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The primary anchor bears 100% of the load
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The secondary anchor has no tension, unless the primary fails
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The system must be properly aligned to prevent shock or extension during failure
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Anchor points must be close to each other to maintain safe load geometry
Though only one anchor is actively engaged, both must be capable of holding the full load—including any impact forces that might occur if the primary fails under tension.
Best Practice Configurations
Below are two recognized setups for slack anchor systems:
✅ Best Practice:
Independent Primaries, Independent Secondaries
Each rope system (e.g., main and belay) has:
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Its own independent primary anchor
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Its own independent secondary (backup) anchor
This offers full separation and clear function across the board. If one system fails, the backup is isolated and fully capable of taking the load without interference.
✅ Better Practice:
Independent Primaries, Shared Independent Secondaries
Each rope system has:
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Its own primary anchor
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But shares a common secondary anchor between systems
This still provides redundancy, but care must be taken to understand how loads could compound if both systems activate the shared backup simultaneously. While not ideal, it’s a functional compromise when space or anchor options are limited.
Critical Considerations
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Pull all unnecessary slack out of the secondary anchor leg. It shouldn’t be tensioned—but it also shouldn’t lag dramatically behind the primary.
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Keep anchors aligned and close to avoid vector errors.
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Primary anchors must never be shared between systems. Belay and working lines may share secondary anchor points, but not primaries.
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Secondary anchors must be strong enough to handle the entire load, including potential shock force from a primary failure.
This is where slack anchors can go wrong—if the second point isn’t truly capable of acting as a full primary under stress, the system fails when it’s needed most.
Final Thought
Slack anchors are not shortcuts—they’re strategic backups. Used properly, they offer clean redundancy without overcomplicating the system.
But they demand precision. Both anchors must be placed with intent, with the second anchor prepared to become the first the moment it’s needed.
Peace on your Days
Lance
