Posted: 04/06/2014 at 16:01
I use string mainly - as David says, the clippy things would be a bit severe on finer Clematis stems. The wire split circles are useful too, but I also buy plastic coated wire on reels and just cut pieces to suit. There's some green rubber/foam covered wire available now (quite thick) which I've not tried but it might look a bit ugly unless there's a good bit of foliage to cover it up. I like doing tying in.
Remember to tie string firmly round the support first, then round the stem loosely to avoid chopping the stems in half