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.