Intuitively you might think that two anchor points will split the load 50/50 in an anchor system. In fact, the geometry of the system determines how the load is distributed in an equalized system.

Consider the diagram at right. Of the four examples, which angle is will create the safest anchor?

When building an anchor system, how can you adjust the angle to ensure that you don't create an unsafe system?

American Triangle

Rather than distributing the load between the two bolts, this setup actually puts greater force on each of the bolts because of the mechanics of the triangle. Doubt it? Get out your calculator, physics and trigonometry book, and look of the chapter on vectors.

What's wrong with this anchor?

What will happen if one of the bolts or carabiners clipped to the bolts fail? What will happen if the webbing fails?

Twist and Clip

By twisting and clipping, the rope's carabiners are clipped into the loop of the webbing so that if one of the bolts fails, at least the loop will catch the rope.

Will this anchor extend if one of the bolts or carabiners fail? How far?

What happens if the webbing is cut by a sharp rock?

Self-Equalizing Anchor

1. In this setup the anchor will equalize in a variety of positions with out having to be retied

Extension!

If one of the bolts or carabiners fail, the loop will catch the rope, but notice the extension that will severely shock load the remaining components of the system.

If you tie an overhand knot in the webbing before clipping it the anchor it will still self- equalize, but won't extend as far as in the preceding example.

Furthermore, if you tie off both pieces of webbing you create redundancy because if the webbing is cut in one spot, the knots keep the anchor intact.

Mmmm....don't have enough carabiners, what to do? (buy some more!)

Girth hitching the bolt as in this picture reduces the risk that it will slide across the sharp edge of the bolt. Maybe OK for rappelling, but DO NOT belay or top rope off of such a setup! Is this anchor system redundant?

Position Equalized Anchor

A quick way to equalize an anchor in a single position is to tie off the entire bunch of webbing with an overhand or figure eight (easier to untie after loading).

Cordelettes are great for building anchors too. You can build position or self-equalizing anchors just as with webbing.

Create a loop by tying the ends together with a double fisherman's or figure 8 follow through, which is easier to untie after loading.

A. These biners are neither opposite nor opposed. It is possible that they could hit on the rock and open simultaneously, significantly decreasing their strength or allowing the rope to pop out.

B. These biners are opposite. Biners that are opposite are less likely to open simultaneously if they slap on the rock, but one of the biners could rotate 180 degrees and you would end up with the situation pictured in A. above.

Bad Idea. This setup creates the dreaded American triangle and the rope will probably be really hard to retrieve because of the friction as it runs through the sharp bolts.

There are at least two problems with this set up.

What happens when one of the bolts or a single chain link fails?

What angle does the chain make between the bolts. Is the load shared or magnified?

Better!

And this rope will be much easier to retrieve.

Okay, you've got a better angle to split the load, but its not redundant because the entire system fails if the webbing breaks or one of the bolts fail.

Better.

Two pieces of webbing, equalized. You might end up with a lot of friction when you pull the rope through that much webbing. It might make it easier to retrieve if you tie in a rappel ring. Costs a little more, but hey, you're worth it baby!