I just came across this video, and although it's in Russian, it doesn't really require any translation. All this guy is doing is making something very useful and strong (as well as long lasting), from an everyday object that we all normally discard! http://www.youtube.com/watch?v=hQeeJEpBYsg For people like us who are always short of ropes and strings to tie in the garden - This method will really save a lot of time and money in the long run. Plus it seems like a lot of fun! Making it only requires a steel blade from a box cutter, which is placed inside a squire aluminum channel - That's just about it!
I must let my eldest son see this as he hates wasting plastic bottles and has been looking for new ideas on how to make them useful.