Flatness 2
The absence of any gap or clearance when a strip is placed, without applying any pressure, between two parallel-faced plates. Wherever a gap exists under this condition, the strip is "unflat". There are two kinds of "unflatness"--thickness non-uniformity (such as frown, profile, etc.) and geometric non-uniformity called shape defects such as (wavy strip, bent strip, coil set, center buckle, etc.).
