Jonathon asked, "have you ever used the 12-point system?"
"The 12-point system?" I asked. "What's that?"
Jonathon explained that it's a system used to evaluate student anchors. The goal is for the powerpoint in each anchor to have a value of twelve. The value is provided by individual pieces. A good cam or a good stopper is worth four-points. So if you have three good cams or good stoppers, you have a value of 12 at the powerpoint.
I have used the 12-point system to teach anchor construction ever since that original conversation. I find that students understand this complex topic far more effectively when it is laid out before them in this way. Following is a breakdown of the 12-point evaluative system:
- --A four-point piece is bomber. It should be able to hold a substantial fall.
- --A three-point piece is pretty good. It should be able to hold a short fall. An example might be taking a fall with your feet at the piece.
- --A two-point piece isn't very good. It will hold a fall with your waist at the piece.
- --A one-point piece is essentially aid gear. It will hold bodyweight, but is unlikely to hold a fall.
- --A large cam, 1" or more -- 4 points
- --A small cam, less than 1" -- 3 points
- --Micro cams -- 2 points
- --A large nut, a Stopper size 8 or greater -- 4 points
- --A medium nut, Stopper 4-7 -- 3 points
- --A small nut -- 1-2 points depending on size and rock quality
- --A very large tree with a good root base -- 12 points
- --A very large boulder that doesn't move and is on stable terrain -- 12 points
- --A good bolt -- 6 points
A simple three-piece pre-equalized 12-point anchor in good rock
Note that you are not required to use lockers in the pieces and that these could have been non-lockers.
This is an anchor "in series." An individual may choose to use this kind of anchor
when there area lot of pieces in the system to obtain 12-points, but a cordellete
isn't long enough to link all the pieces together. In this photo there are
only three pieces, but there could easily be five, and they would be dealt with the
same way, by building anchors on top of anchors.
You should only build your body into a 12-point anchor if you need to do so for speed on a very big objective, or you cannot build a system that meets or exceeds 12-points. When you belay off your body it is difficult to escape the belay if anything went wrong...and if you're anchor is terrible, then a belay escape isn't really an option anyway.
There is only one magic bullet when it comes to building a good anchor, and that's experience. The concept of a 12-point anchor will provide you with a good foundation for anchor building, but to really feel confident, you're going to have to build a lot of anchors...
--Jason D. Martin