Corrugated Packaging Reference Materials: Structure

The basics of box-making

Architects have known for thousands of years that an arch with the proper curve is strongest way to span a given space. The inventors of corrugated fiberboard applied the same principle to paper when they put arches in the corrugated medium. These arches, known as flutes, are anchored to the linerboard with a starch-based adhesive. They resist bending and pressure from all directions.

When a piece of combined board is placed on its end, the arches form rigid columns, capable of supporting a great deal of weight. When pressure is applied to the side of the board, the space between the flutes acts as a cushion to protect the container’s contents. The flutes also serve as an insulator, providing some product protection from sudden temperature changes. At the same time, the vertical linerboard provides additional strength and protects the flutes from damage.

Corrugated Flutes



E-flute has a thickness of 1/16 in.; 90 flutes per foot

B-flute has a thickness of 1/8 in.; 47 flutes per foot

C-flute has a thickness of 3/16 in.; 39 flutes per foot

A-flute has a thickness of 1/4 in.; 33 flutes per foot

Double wall has varied flutes, which provide advantages over flutes of the same size that are perfectly aligned



In general, larger flute profiles deliver greater vertical compression strength and cushioning. Smaller flute profiles provide enhanced structural and graphics capabilities for primary (retail) packaging.

Learn about corrugated box printing and corrugated box styles.

Information and illustrations used with permission from the Fibre Box Association. Fibre Box Handbook is copyright ©2005 Fibre Box Association. All rights reserved.