sparkfun Raspberry Pi Zero Wireless Camera Kit Setting Up page 9

Here's the sandwiched servo. Again, note the orientation for proper assembly.
Here, you can see where the screws identified a couple of steps ago fit into our servo sandwich. Tighten them
down, but not too much.
Now fit the shaft of the servo into the fitting on the horn that you previously installed into the base. This is the point
where you need to make sure that the shaft is roughly centered in order for the entire assembly to work properly. I
do this by turning the shaft all the way to one extreme, then turning it 90 degrees back in the other direction. Then,
I remove the base and line it up with the body of the servo motor.