The corrugated PAD, also called corrugated cardboard, is characterized by combining two elements in its structure: One (or several) corrugated paper sheet, also known as a flute or medium, which acts as a central nerve and provides the corrugated cardboard with an extra of resistance If we use the simile of a sandwich, this component would be the ham or sausage that we place inside. Plain cardboard sheets (or liners), which are placed on the outside or that work as separators for different layers of flutes. Following the example of the sandwich, the liners would be bread.