Architects discovered long ago that an arch with the proper curve is the strongest way to span a given space. Corrugated sheets have evolved with this basic principal in mind. The fluted medium is bonded to the liners with a starch adhesive. Once bonded the combined board resists bending. The flutes provide cushioning when pressure is applied from the sides and when placed on end they form rigid columns capable of supporting a great deal of weight.

The most commonly used flutes are C and B flute. Others include A, E, and F flute. Specialty micro-flutes have been recently created to form specialized grades capable of competing in the boxboard market. Generally, larger flutes offer greater vertical compression strength and cushioning. Smaller flutes offer printability advantages as well as structural advantages for retail packaging.

Standard Corrugated Flutes

Flute Designation*	Flutes per Linear Metre	Flute Thickness (mm)	Flute Cross Section
A Flute	108±10	4.76
B Flute	154±10	3.18
C Flute	128±10	3.97
E Flute	295±13	1.59