A Long Splice
As a very young Tower Captain, I realised that our ropes were wearing out where they ran through the pulleys. Having no tower fund, I decided I'd have to repair them all. I had never done a splice before, but I had a really ancient, dog-eared book that told me how to do it. Quaking in fear, I cut each of our ropes and turned the top rope upside down so that the good rope from around the wheel was above the sally. Luckily the Scout Bellringers' book explained it all well enough that the operation was successful. I don't know what I'd have done if I'd ruined a rope!
Just in case you find yourself in the same predicament, here are the instructions from the book that saved me.
PS. Don't cut the rope too close to the sally!!!