Dum question on 993 seat heating

I now have my new 993 seats in the car and working. The electrical hight adjustment is easy enough to figure out, but the heating isn't - at least not for me There's a bottom which can be pressed 2 ways and in the middle of it there's a "roll" (no idea what you call it in english?) which is probably meant for infinetely variable heating control? Exactly how is this meant to work? I tried fiddling with the contacts, but my seats were already burning hot from standing in the sun so I couldn't feel any difference.

Is there a 993 owner here who can enlightned me on this subject?