In reply to worthy1:
>
> how do setters know what kind of routes to set for any particular grade
>
> I assume there has to be some refence point to ensure some consistency across the various walls.
This is my first year of semi-professional routesetting (in france).
I'd say it depends a lot on the wall. Three different walls in the same area might feel like three different crags, and i think it is positive.
So the most important reference points come from the wall itself i'd say:
-walls lenght, inclination, features
-what holds are available?
-who climbs at this wall? What do they expect? What do they need? What do i want to tell them?
Then, when the job is enough paid not to be an amateur thing, there can be some specific directions.
Eg, the routesetting manager might ask that you set a "commercial 6a" (=ladderish, it's only the holds size and spacing that make it 6a) or a "technical 5c", and will also give general directions such as "our clients don't like dynos. No dynos before 7c" or "always be sure that someone 5 ft tall will reach", etc...