Answer
Before placing magnetic signs on any surface, it is important to carefully read and follow the care instructions. All magnets should be correctly prepared and flattened before placing them on any metal surface. The full care and installation instructions can be found here:
Magnetic Signs Installation Guide.
Very Important! – Lay your car magnet out flat first. If not, it will not stick to your vehicle for a prolonged period of time. Magnets are extremely-pliable and susceptible to bending or wrinkling during the shipping process.
Magnetic signs should be placed on a refrigerator door for at least 24 hours to flatten and re-magnetize them after shipping. If they will not stay on the refrigerator, lay them on a flat surface for 24 hours and then on the refrigerator for another 24 hours.
Magnetic signs should always be stored flat with nothing placed on top of them, and never stacked on top of one another. They should be removed, cleaned, and inspected daily.