In our industry we like to make sure that we are always 100% tied in. We also like to make sure that all our systems are backed up. This is exemplified by the way we descend. We choose two solid anchors and make sure that we tie in with two ropes.
The problem with this system is if the climber hangs, the primary rope rarely positions us where we need to work. In this scenario, using the tower legs, we will always be pulled to the side of our primary system. The second problem is if we ever become detached from our primary, we will swing to the anchorage on our secondary. Not only would the swing risk injury, but depending on the angle of the secondary rope, it may take several feet for the rope grab to lock, increasing the climber’s fall distance.
Now let’s look at another possibility:
This system uses the same two anchor points and anchor straps. However, instead of a figure 8 at the end of each rope, there is a Canadian 8, or Bunny Ears. With the Bunny Ears, we can attach to both anchors simultaneously. This system has several advantages. First, by using Bunny Ears it allows both ropes to be centered where the climber needs them.
Second, it makes the anchorage truly redundant and not parallel. This means if one single anchor point failed, the climber would still be attached to both ropes and have control over their descent. In the even that the climber became detached from their primary, they would fall straight on to their secondary.
Using the same anchorage and replacing the Bunny Ears with a Figure 8 and an Alpine Butterfly, the system becomes more directional. This configuration is also useful when the anchor points are further apart.
For added security, a secondary carabiner can be added to both ropes. Keep in mind that only one rope is used at a time, so the secondary rope is not actually applying force on the system until the climber becomes disengaged from their primary rope. The second carabiners would be a necessity if the angle of the anchors became too great. They can be installed opposite and opposed, to prevent rollout.
There are many different configurations for anchorage. I prefer just to teach a few, so that everyone can learn primary systems. This way, everyone can learn to confidently set up anchors. And more importantly, coworkers can easily perform checks on the system.