In many rescue environments, a fully redundant system is needed—but the available anchors may be limited. One efficient solution is a Slack Anchor System with independent primary anchors and a shared secondary anchor. This setup preserves redundancy without requiring four completely separate anchor placements.

It’s a hybrid model: strong, efficient, and commonly used in rope access, industrial rescue, and alpine settings.

What Is a Slack Anchor System?

A slack anchor system uses a primary anchor that is fully tensioned and load-bearing, with a secondary anchor that remains unloaded until a failure occurs. The second anchor functions as a backup and must be able to handle the entire load if needed.

Independent Primary + Shared Secondary Setup

In this configuration:

• Each rope system (mainline and belay) has its own independent primary anchor

• Both rope systems share one common secondary anchor

This structure reduces clutter, saves gear, and allows full system redundancy with just three total anchor points instead of four.

Step-by-Step Overview

1. Establish Primary Anchors

   • Choose two strong, independent anchors for your main and belay lines

   • These anchors should be appropriately aligned with the fall line

   • Each system is rigged to operate independently under normal load

2. Configure Shared Secondary Anchor

   • Identify a third solid anchor that is easily accessible by both systems

   • This shared point serves as a backup if either primary fails

   • Use separate connection material for each rope to maintain isolation

3. Apply Slack to the Secondary Anchors

   • The shared secondary anchor must remain unloaded until activated

   • Ensure minimal slack to reduce extension if a transfer occurs

   • Slack should be controlled and purposefully introduced—not left loose

Why Use a Shared Secondary?

• Efficiency: Reduces total anchor placements from four to three

• Space Saving: Useful in constrained or cluttered anchor zones

• Redundancy Maintained: Full backup capacity with clear load path logic

• Cleaner Rigging: Fewer components, less confusion in edge operations

Key Considerations

• Shared does not mean compromised — the secondary must be as strong as the primaries

• Anchor geometry matters — all three anchors must be aligned to minimize angle-induced force multiplication

• Monitor slack — too much slack can cause shock load; too little may interfere with primaries

• Pre-plan for failure — if either primary fails, the system must redirect cleanly to the shared secondary without crossover

Use Cases

• Rope access in industrial sites with limited anchor options

• Alpine or canyon terrain where placements are scarce

• Any scenario where gear weight, simplicity, or space matters

• Environments where quick re-rigging or system isolation is a priority

Final Thought

The Independent Primary, Shared Secondary Slack Anchor System is a smart compromise—blending redundancy with practicality. When configured intentionally, it reduces gear load while preserving system integrity.

It’s a perfect example of how experienced riggers adapt to terrain, time, and gear limitations without sacrificing safety.

More Anchors… 

Peace on your Days

Lance