We keep finding and replacing anchoring points that were made impractical by the accumulation of quick links. On this image, you can see an anchoring point in which the ring was in perfect shape and did not require any additional link. It means that the climbers could not thread a close ring. 

If you cannot thread an anchoring point please leave a carabiner, so the next climber can remove it. Or, even better, join up a proper climbing course before climbing outdoor!