It can be done with a pole by `trad`it`s as
Peter Fogwill says.But if there`s a sill or a ledge
of any depth ya need a `Ledger` or a combined
tool called a `LedgerMate`.A BackFlip won`t
do it unless there`s no ledge at all much.I`ve one commercial account who prefer `LedgerMates` as opposed to pure water.Funnily enough I`ve thought a few times about going back to `pole-trad`but the future
of the W.F.P side of things intigues me no end.