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.).
