Load-limiter knots and chaining
In the mountains or on long rock routes, anchor efficiency can be the difference between a comfortable finish and a forced bivouac. Using a cordelette to equalize an anchor is easy and strong, but it takes a lot of extra time to set up, and even longer to break down. There is a faster, easier, and often equally safe solution: the "alpine anchor.”
An alpine anchor “chains” pieces by clipping together the full-strength loops and slings on nuts, cams, or fixed pro. These anchors are equalized, redundant, and have very little or no extension. Examples:
Clipping two or three cams and nuts in a row with nonlocking carabiners(1); your master point is in the lowest of the cam slings.
Clipping two cams or nuts together, equalized with a third piece via a sling.
Incorporating a horn or tree by throwing a sling around it and equalizing with one or two pieces of protection (2).
To equalize alpine anchors, many climbers create a socalled “magic X” (aka “sliding X”) by putting a twist in one strand of a sling connecting two pieces of protection. This system has the advantage of “auto equalizing” the pull on the pieces as the belayer moves around. The disadvantages are that the magic X is not redundant, and in most cases the slings climbers use are weaker than the bolts or pieces of gear they are equalizing. Why double up on what’s strong— the protection—and not on the weaker slings?
There is a simple answer: Load-limiter knots make the anchor completely redundant but still offer some range of auto adjustability.
First, clip the ends of the sling to the pieces of protection you are trying to equalize. Grab both loops of the sling and pull downward to gather them at the center. Twist one of the strands of sling to create a small loop, and clip a locking carabiner through this loop as well as the other strand (3). Pull this master point side to side to make sure it’s clipped correctly and equalizes the load on the anchors. This is the magic X.
Now unclip one strand from the protection and tie a load-limiting overhand knot a short distance above the master point. (4) Reclip to the pro. Repeat the process on the other side. If the protection at one end of the anchor sling fails, these knots will limit the sling’s extension and thus the amount of force the other anchor(s) have to bear.
If you don’t have enough sling to tie two load-limiting knots, put one in the longer arm of the sling. This will limit shock-loading in case the piece farthest from the master point fails, but there will be no redundancy at the clip-in point.