Summarize this article in one sentence.
Cardboard is simply a sheet of ridged paper sandwiched in between two sheets of flat paper. The corrugator organizes and assembles the three different sheets to make corrugated cardboard. The ridged paper increases the stability and durability of the cardboard while using a relatively small amount of paper. The machine heats the flat paper to 350 degrees Fahrenheit and pushes it through ridged rollers. The result is a sheet of paper with a repeating U-shaped design that will be used as the core of the cardboard. The corrugator applies a starch-based glue to one side of the ridged sheet, which is then pressed onto a sheet of flat paper. The same process is used to apply another flat sheet to the untouched side of the ridged sheet, creating the familiar corrugated sheet of cardboard. Further cuts and perforations are made to allow for folding into various shaped boxes and containers.

Summary:
The industrial process of making cardboard boxes uses a machine called a corrugator. The ridged sheet is made by running paper through the corrugator. A flat sheet of paper is glued to each side of the ridged sheet. The large sheet of corrugated cardboard is then cut based on the desired size and shape.