Also known as corrugated cardboard. It is made of at least one layer of corrugated paper and one layer of boxboard (also called boxboard), which has good elasticity and extensibility. Mainly used in the manufacture of cartons, the center of cartons and other packaging materials for fragile goods. It is mainly made of native straw pulp and waste paper by beating to make the original cardboard similar to yellow cardboard, and then rolled into a corrugated shape through mechanical processing, and then bonded with the boxboard paper with an adhesive such as sodium silicate on the surface.