What mysterious force holds the plastic pizza signage to the top of this moving car?
The attached photo was taken recently at an undisclosed location, somewhere in the Former United States (FUS). In it you can see a plastic sign-thingy on top of a moving car. My question is this: What mysterious forces keep the plastic sign-thingy from sliding off the car due to the effects of wind and inertial pseudoforces. What holds the sign to the top of the car? Is it powerful magnets? Double-sided sticky tape? Is it perhaps... love? Has anyone seen one of these artifacts up close, and/or knows for sure what the physical mechanism is?