Flute
The wave-shaped medium inside corrugated board, and the size class of that wave (A, B, C, E, F).
In practice
Flute size is identified by how many flutes fit in a linear foot. Larger flutes give thicker board and more stacking strength; smaller flutes give flatter print surfaces and better puncture resistance per thickness.
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Related terms
- Medium
- The paper that is fluted on the corrugator and sits between the liners.
- Caliper
- The thickness of a sheet of board, usually given in inches or millimetres.
- Take-up factor
- How much more medium goes into a length of board than the board's own length, because the medium is fluted.
- Corrugator
- The machine that forms the fluted medium, glues it to liners and cuts the combined board into sheets.
- Print surface
- How flat and smooth the outer liner is for printing.
Definitions written by Packgent, last reviewed 2026-10-27. All terms.