How to make a simple handmade refrigerator.

Materials required: a double-layered box and an appropriate amount of sand. Production steps:

1. Find a double-layer box with good sealing.

2. Put sand on the outermost layer.

3. Put the items to be kept fresh in the inner layer and seal it with a lid.

4. Place this device in a cool and ventilated place, and add water to the outer layer frequently to keep the outermost layer moist.