A closed-looking lid may have an edge gap. Use a maker specification or approved packaging trial.
Inspect the empty box
On a level surface, let the lid settle without force. Inspect four edges in order; note rocking.
Use a consistent criterion
Use a defined criterion's gauge or method. Random paper will not give consistent results.
Separate the loaded trial
A liner or load may affect seating. Check with the approved reference load; tape can hide a gap.
