In reply to Timmd:
> Without a guide book it's still on-sight for the person climbing an established route, even if it has been gardened and climbed before, and changed. It's still on-sight for them, in them not knowing about hidden holds or tricky moves and things.
> That's aimed at the person you're replying to...
Depending on the crag, far less so. There may be chalk on holds indicating/telling you where holds are, especially nominally hidden ones. There may be an obvious worn/traveled path showing you where the route goes, and again possibly indicating where holds are. So, arguably, at least at moderately well-traveled crags, even without a guide book you aren't truly on-sight climbing since you do have some beta about the route. (Personally, I'd consider such climbs, and even ones where you used a guidebook to find a climb an have some idea what grade it goes at, etc, to be on-sights. But from an ultra-pure definition of it, it is arguable that climbing any route that is visibly established is not an ultra-pure-true on-sight.)