Profile of a surface (⌓)
Profile of a surface (⌓) puts a uniform boundary around the exact designed shape of a surface, and the whole surface has to lie inside it. With datums named, it also controls the surface’s orientation and location.
Easily confused with
How to read it
The symbol is a semicircle closed by a straight base line. The National Physical Laboratory’s guide describes the tolerance as a uniform boundary along the true profile within which the surface must lie, and Keyence draws it as the two envelope planes traced by a sphere of the tolerance diameter centred on the exact surface. The zone can sit equally either side of the true profile or to one side, depending on how the frame’s leader is drawn (NPL). In Berez’s ASME notes, profile can govern location, orientation and size as well as form. Cogorno adds that a profile of a surface frame usually names datums so that it can orient and locate the surface, and ASME’s description of Y14.5-2018 says the revision emphasizes profile for locating surfaces.
Also searched as: ⌓, profile of a surface gd&t, profile of a surface symbol.
This explains what a symbol specifies on a drawing. It isn't inspection or design guidance; the drawing and the edition of the standard it cites take precedence.
Marks that go with it
A profile frame often comes with extra marks. Cogorno’s guide lists the “all around” symbol, where the tolerance runs all around the outline of the part (Unicode has it as ⌮, U+232E ALL AROUND-PROFILE), and the “all over” symbol, two small concentric circles where the leader bends, for a tolerance over the entire surface. A circled U after the tolerance means the zone is unequally disposed about the true profile.
Differences by standard
For an unequal zone, ASME drawings use the circled U and ISO drawings the letters UZ (Keyence). Unicode annotates the symbol, ⌓ (U+2313) SEGMENT, as “position of a surface”.
Look-alikes
Profile of a line ⌒ is the open arc without the base line, and controls single cross-sections.
Read next
- Next in GD&T symbolsAngularity (∠)Angularity (∠) is an orientation tolerance: a surface or axis meant to sit at a stated angle to a datum has to lie in a zone tilted to exactly that angle. It needs a datum.
- The same shape in Accessibility symbolsAssistive listening symbol (ear)An ear with a diagonal bar across it is the International Symbol of Access for Hearing Loss. It marks an assistive listening system: a loop, infrared or FM system that sends sound to hearing aids or headsets.
More GD&T symbols
The same shape elsewhere
Browse symbols drawn with curves and waves or lines.
Sources
- Fundamental Good Practice in the Design and Interpretation of Engineering Drawings for Measurement Processes, Measurement Good Practice Guide No. 79, David Flack and Keith Bevan, 2005, National Physical Laboratory (UK), Chapter 4, Profile
- Geometric Dimensioning and Tolerancing for Mechanical Design: Instructors’ Guide, Gene R. Cogorno, guide to the McGraw-Hill textbook, rev. 10/12/2020, Technical Training Consultants, Chapters 3 and 11, review answers
- Form Tolerance and Location Tolerance (Profile Tolerance of Line / Profile Tolerance of Plane), GD&T Fundamentals, KEYENCE America, Profile tolerance of plane
- GD&T Symbols, GD&T Fundamentals, KEYENCE America, Associated Symbols
- Y14.5 - Dimensioning and Tolerancing, ASME Y14.5-2018 (R2024), standard description, ASME, Description
- Fundamentals of Geometric Dimensioning and Tolerancing (GD&T), Part I, Jaime Berez, seminar adapted from an undergraduate mechanical engineering course, version 2.1.0, 2023, Center for Precision Metrology, University of North Carolina at Charlotte (Zenodo), Slide 36
- Miscellaneous Technical, Range: 2300–23FF (code chart), The Unicode Standard, Unicode Consortium, U+2313, U+232E
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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