Scenario: You and a relatively new climber friend are sport climbing. You’re leading the routes, your friend is following and lowering, and then you’re climbing the route a second time to clean the anchor.
It's getting on toward the end of the day, you're getting a little tired, and you don't feel like climbing that last route a second time.
You need to get your anchor gear back, but your partner doesn’t know how to safely clean the anchor and either rappel or lower off In the standard manner.
Fortunately, there’s a Crafty Rope Trick (CRT) to rig the anchor when you’re leading to make it quick and safe for the second to clean and lower.
When you arrive at the anchor, you do the following:
Rig the rope through the bottom rings on the chain and prepare to be lowered.
Add two locking carabiners about 3-4 chain links up from the rope.
Clip the rope through these two locking carabiners.
Now, you can top rope all day long off of this anchor. All of the weight of the climber will be supported by your carabiners, not by the bottom rings of the chain, minimizing wear and tear on the fixed hardware.
(Truth be told, you can do this with one locking biner as well.)
When your inexperienced partner makes it to the anchor, all they do is clean the carabiners and call for a lower. The rope is already rigged for a safe lower through the bottom rings of the chain. The second never comes off belay or unties; all they do is unclip two carabiners, which is hopefully within their abilities.
Yes, you old-schoolers, with modern anchor hardware, it is acceptable practice to lower the last climber off of the chain rings. This is per the recommendation of the American Alpine club, so please don't argue with me on this one.
To clarify, lowering off of fixed gear is only for the LAST person, not everyone who is top roping the route.
1 - Rig the rope through the bottom rings on the chain.
2 - Add two locking carabiners about 3-4 chain links up from the rope.
Clip the rope through these two locking carabiners. (Yes, anchor engi-nerds, the angle of the rope through the carabiners is not optimal, but it'll work.)