Cadillac STS 2011 Owner's Manual page 446

WARNING: (Continued)
To be even more certain the vehicle will not move,
you should put blocks at the front and rear of the
tire farthest away from the one being changed.
That would be the tire, on the other side, at the
opposite end of the vehicle.
When the vehicle has a flat tire (B), use the following
example as a guide to assist you in the placement of
wheel blocks (A).
A. Wheel Block
B. Flat Tire
The following information explains how to use the jack
and change a tire.
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