I just use dental floss. I wrap it around a set of different needles and put it in my PSK. It has excellent tensile strength. It is waxed. I've repaired blown out backpack straps with it among other things and it hasn't failed yet (actually, the old pack is stronger now). I fashioned a water jug carrier out of denim shorts using it once. It actually permanently reinforces any el cheapo quality stitching on any chew toys my dog makes quick work out of.