Bertha Berman invented the fitted bed sheet on October 6, 1959. She realized that a mattress needed a cover so it would not get spoiled. However, without the elastic placed on the corners of the sheet, it would not stay attached to the mattress. Thus, Bertha came up with the idea of attaching elastic to the corners that would hold down the sheet when a person moved in their bed. Patent us2907055 is the patent Bertha got for her invention. You can find her sheets in hotels, homes, and stores across North America. Now, do you know how to fold it?