Steering Adjustment

[grantsauder]

I had to remove the steering assembly from my late 31 CCPU to adjust the steering play which was in excess of 2 inches. It is a two tooth unit. I did all
the adjustments as as instructed in the Model A Ford mechanics Handbook Vol. 1. It mentions the centralization rivet slot is normally set in the vertical position.
Question: What does the adjustment from the vertical position control? more info is needed so as to fine tune the steering assembly.
Thanks for your welcome info. Grant