I have grown blackberries for several years using traditional metal wire for trellising and its always been a pain. I put in several raspberries last year and wanted to do a better job of trellising them and found this monofilament wire.
http://www.orchardvalleysupply.com/products/vineyard-monofilament-wire
Its similar to weedwacker string and dosent need any hardware!
you just use their special knot which is just wrapping the excess up then down the wire and sticking it through. Do it on both sides and your done.
heres a shot of the whole thing, I know its not much to look at right now, I put in three bare root heritage raspberries last year but this will just be a wall of canes this season.
I just wanted to share how awesome this stuff is, really easy to work with and no extra hardware. I got really lucky today actually and the whole install only took like 45min I think.
http://www.orchardvalleysupply.com/products/vineyard-monofilament-wire
Its similar to weedwacker string and dosent need any hardware!