If the box can't be opened, you can insert a fruit knife into the gap of the lid to let the air flow in. The cooled box can be soaked in microwave oven or hot water. Let the air inside expand when heated. The heated box can't be opened. You can wait until it is completely cooled or pour a little cooling on it to let the temperature in the box drop.

a packing box is a plastic box when ordering take-out. It is more convenient and portable than a plastic bag, easy to carry and not easy to spill. It can be used for rice, vegetables, hot and cold dishes, fried chicken and other delicious foods. In restaurants, or small restaurants, boxes for eating leftovers are called packing boxes.