Flatness

Flatness at U+23E5 is a technical symbol used to indicate that a surface must be flat within a specified tolerance. It belongs to the Miscellaneous Technical block and is most often seen in engineering drawings rather than ordinary text. Its main role is in geometric dimensioning and tolerancing, especially in mechanical design, manufacturing, machining, and inspection documentation. A callout using ⏥ followed by a tolerance value tells the maker or inspector how much a face may deviate from an ideal plane, such as requiring a machined plate surface to remain flat within 0.05 mm. The symbol appears in CAD drawings, product definition data, quality-control reports, and standards-based drafting notes that follow GD&T conventions such as ASME Y14.5 or ISO GPS practice. It concerns the shape of a single surface, not its angle, position, or relationship to another datum, so it is different from parallelism, perpendicularity, or profile controls. Because it is a specialized drafting character, some engineering fonts and CAD systems may substitute their own glyphs or use symbol libraries instead of plain text. In searchable documents, using the actual Unicode character can help distinguish the flatness control from the spelled-out word “flatness.”