One such fold down box is used by a famous pizza company. When the pie is put in hot, a sensitive 'spot' on the container changes color. If it goes back to the original color before it is delivered, that is if it cools down too much, the pie is give free of charge. This keeps the delivery guy on his toes but it is also a great incentive for the customer to keep coming back for more. What a cool way to entice people!