flute

Inverted S-shaped 'arch' or 'wave' of a corrugated medium that normally runs parallel to the depth of the container and gives it the rigidity and crushing (stacking) strength. The major five sizes of flutes are: (1) A-flute: the highest arch size, between 32 to 37 flutes per foot. (2) B-flute: second highest arch size, 45 to 52 flutes per foot. (3) C-flute: intermediate between A and B, between 39 to 43 flutes per foot. (4) E-flute: has 92 to 98 flutes per foot. (5) F-flute: the latest flute size, about 128 flutes per foot. [D-flute is no longer made.]