Two weekends ago I had only my second climbing experience on routes that have been rated. Prior to that, all of my ascents have been free climbs on backcounty Adk slides which I merely assumed topped off at Class 4. Based on the rated routes I recently climbed, I now realize that some of these slide pitches have been low to mid Class 5. I also realize there is a big difference between a 5.4 friction and a 5.4 vertical climb (at least to me). So I was wondering for future reference, is there a basic set of rules for rating friction climbs?

short answer: no.

Don't assume there's a clear distinction between fourth and fifth class, either.

Well, there is one guideline: a 5.6 friction climb tends to be steeper (or on a more slippery rock type) than a 5.3 friction climb.

is there a basic set of rules for rating friction climbs?

yes, do some established friction climbs & you'll know what your new route should be roughly rated.

^^^ what rpc said, especially get on classics, i.e. routes established by Fritz Wiessner and alikes. Also, I think by 'free climbing' you meant 'free soloing' or unroped travel.

Shet, Fk, Motherfker and Fk That.....

The Chief wrote:Shet, Fk, Motherfker and Fk That.....

You need to work on your spelling skills.