There are two kinds of shadows to look out for in camouflage.
One is the concealing shadows cast by objects or formations on the
ground. From the air these shadows appear so dark that a vehicle
parked within them has a good chance of being unnoticed. Other
camouflage measures should often be taken, but making use of these
shadows is an important primary step in concealment. In the northern
hemisphere, the north side of an object higher than the vehicle is the
best side to park on, and the east and west sides are each dangerous
for half a day.
The other kind of shadow to look out for is that cast by the vehicle.
This reveals and identifies a vehicle and must be hidden. Hiding is
accomplished either by parking in the shadow of an object—if the
shadow is large enough to encompass the vehicle—or by parking on
the sunny side of the object, if the shadow is too small. Watch out
not only for the over-all shadow of the vehicle but also for the
smaller shadow areas contained within the vehicle itself, such as the
shadow line of the truck body, in and around the cab, underneath
the fenders, within the wheels, and in the open back of the cargo
space. A vehicle is easily recognized by these small shadows even
when its main outlines are obscure. They must be broken up or
hidden by natural or artificial materials.