Just thought id post up a little alternative to glow light markers for your tarp lines. These are little led units i knock up. All you need is a CR2032 lithium battery (£1.48 for 10 delivered on evilbay) a bog standard 3mm or 5mm led of your choice (pence on evilbay but dont go to maplin) and a couple of neodymium disc magnets (couple of quid on evilbay)
put the led legs either side of the battery (longer leg is +) put a magnet on one side to secure the leg to the battery, slip over your line and then add the second magnet. The last one of these i timed went for 5 days on one battery (that was a 3mm led). The only thing you will need to replace is the battery and at 14.8p for 5 days its pretty cheap.
put the led legs either side of the battery (longer leg is +) put a magnet on one side to secure the leg to the battery, slip over your line and then add the second magnet. The last one of these i timed went for 5 days on one battery (that was a 3mm led). The only thing you will need to replace is the battery and at 14.8p for 5 days its pretty cheap.