Materials
Flute
A flute is the wave-shaped paper layer within corrugated board; flute profiles describe its height and spacing.
What it means in packaging
Profiles such as B, E and F are used to describe corrugated constructions. They influence thickness, folding and surface behaviour, but actual caliper and strength depend on the complete board specification. Flute direction also affects how a blank converts.
A practical example
Changing a mailer from one flute grade to another can require different wall allowances and fold clearances.
What to check
Use the actual caliper supplied for the chosen grade, and confirm flute orientation on the production sheet.