I see your reflective guy line, and I raise you *fluorescent* reflective guy line:
http://www.cleats.co.uk/home/details.asp?id=27Those guys also sell some funky rope cleats that are supposed to be particularly useful.
I bought a pack of 4 pieces (3m, or 9ft each). One piece will be for the front guy line on my tent, two are spare, and the last I cut into 13cm (5") pieces to make highly visible zipper pulls on my backpack.
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