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Material thickness and clearance
Use a measured thickness and a deliberate allowance, and read the limitation for the selected structure.
Reviewed October 27, 2026
Thickness is a material measurement
Where present, Material thickness is the sheet caliper in millimetres. It is not GSM, a percentage or a generic paper-strength setting. Use a reliable value for the actual stock; the 0.30 mm example is illustrative.
The simplified tuck-box and two-piece models adjust fold-line spans using that value. Sleeves also use it when estimating the panel band around an opening. Structures with explicit fold-line or flat-panel dimensions do not pretend to provide the same compensation.
Clearance is chosen space
A per-side clearance adds room to both opposite sides. A two-piece base estimated at 100.6 × 70.6 mm outside receives a 101.6 × 71.6 mm lid opening when clearance is 0.50 mm on each side.
Envelope clearance is applied around the insert's edges. Read the label and model note before transferring an allowance from another structure. Increasing lid clearance leaves the original base inputs unchanged.
Respond to the specific constraint
The model checks whether tabs, curves and wall relationships remain usable within its supported range. An error can depend on another field, so a value that worked in a large box may be rejected in a shallow one.
Real stock bends over a radius and can compress at a score; glue and coatings add local thickness. Check the print scale, assemble a trial and let the joints settle before judging fit. The control is an explicit approximation, not a promise of a perfect manufactured result.
Sources and methods
Ready to make something?
Set the dimensions. Check the folds. Make a small test box.