The dash knobs adjust the vertical. There's also a less obvious smaller knob under the vertical knob to adjust each side horizontally.
My, my, my. I thought you were being a smart-alec, because I had never seen any horizontal adjustment knobs. Lo and behold, they are not "under the vertical knob" on the dash, exactly, but next to the headlight boots. The left one is at about the 4:30 postion to the left headlight boot, and the right one is at the 10:30 postion to the right headlight boot.
THANKS! Even some of us old dogs can still learn a new trick.