The corrugated box commonly referred to as a cardboard box or fiberboard carton is made up of pieces of linerboard on the outside and paper medium in the middle, like a sandwich. Linerboard is usually flat and used mainly for the side exposed to the elements while paper medium is wavy “fluted” material. The more layers of linerboard and medium there are the stronger the box will be.

Single Face – One liner, single medium
Single Wall – Two liners, single medium
Double Wall – Three liners, double medium
Triple Wall – Four liners, triple medium

Flute profiles vary in type of application being used and can be used in combination to tailor fit the box to the customer specifications.

F-Flute: 125 flutes per foot, > 1mm thickness; fine printing
E-Flute: 90 flutes per foot, 1.5mm thickness; retail packaging
C-Flute: 39 flutes per foot, 4 mm thickness; general/ all purpose use
B-Flute: 47 flutes per foot, 3mm thickness; ideal for canned items
A-Flute: 33 flutes per foot, 5mm thickness; greater cushioning due to the thick walls

Measurements are taken from the inside rather than outside as some boxes may use different flutes in the overall construction:

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Length – always the longest of the measurements
Width – always the shortest of the measurements
Depth/Height – distance between the openings

Outside dimensions will be more important to when dealing with pallets, warehouse space or shipping companies.

Box Certificates and Tests

A box’s ability to withstand external or internal pressure is measured in lbs. per square inch, which is given be a Mullen value or bursting test whereas the Edge Crush Test (ECT) is in lbs per inch and measures the stacking strength of a box until it collapses. The higher the numbers the stronger the box.

Interiors

Interior forms a.k.a build-ups, dividers, partitions can come in multiple shapes and sizes that either secure the contents, separate or create voids within the box which may or may not affect the overall strength of the box.