Runco RS-900 Owner's Operating Manual page 54

Installation
Adjusting the Pitch (Angle): Next, angle the lens to even out any top-to-bottom
pincushion distortion. To do this, loosen the Pitch Adjustment T-Screws (directly below
the Height/Y Adjustment T-Screws) on either side of the lens to allow it to pivot freely.
Then, adjust the anamorphic lens angle so that the projected image is rectangular:
Incorrect Lens Angle
The anamorphic lens will almost always be angled with respect to the projector; this is
normal.
Once the proper lens angle has been set, firmly tighten the Pitch Adjustment T-Screws to
secure the lens in place.
There may be some pincushion distortion even after the lens is
Note
properly adjusted, especially at shorter throw distances. If this is the
case, Runco recommends that you slightly over-scan the image
into the screen frame area to mask the distortion.
Adjusting the Yaw: Loosen the Yaw/X-Adjustment Levers to allow the lens to pivot freely
from side to side. Then, angle the lens to even out any left-right pincushion distortion:
Anamorphic Lens (Top View)
40
Correct Lens Angle
Runco RS-900 Owner's Operating Manual