OK, I got it. I think I had something a bit different in mind, like this one:
http://parts.digikey.ca/1/1/10411-rotary-dip-switch-bcd-w-shaft-a6a-10rs.html
(this is what I have).
Googling for "rotary encoder" results in wildly different things than the one from the first link on this thread.
I think it should have been called "rotary switch" rather than "rotary encoder" in the first place. I guess that the wording "encoder" comes from the fact that the switch position is returned as BCD (on 4 bits), so one would need a decoder to interface it with a system.
The rotary switch pictured above has a zero position (among 9 others, numbered). You can rotate it both directions and the rotation is not very smooth (wouldn't make a good volume control, from this perspective). The only application I can see for these would be some (mostly) static/predefined settings, like a temperature threshold, or for setting some voltage or frequency level. And since the writing on them is pretty small, I would like to have some feedback, eventually showing a meaningful value rather than a number between 0 to 9.