In reply to Lee 76:
If you mean as in roped solo ( top rope style ) then I would say if you back it up for example with a prussik or similar then yes but have a good look through the forums here ( use the search function on top right ) .
I use a Wild Country ropeman MK 2 and much prefer it to using a Petzl Shunt or a Gri Gri , a lot of people use a chest harness and other chest type ascenders but I found this quite restrictive .
I must emphasise that you back it up with another device I would say that is imperative . I use it on a 10 ~ 11mm static rope . If you are not sure ask , ask & ask again .
