I thought I'd share this. I've been using yarn for repairs and strengthening weak locs. Why? Because it's incredibly light weight and when your locs are thin, the last thing you want is extra weight on them. It works quite well. I wrap it round a loc as if I'm threading the hair, just as you would using fake hair. I leave a little overhanging the end of a loc in case I want to pull it off later. I see it as a temporary fix rather than a permanent one.