Straightness tolerance symbol

A single straight line inside a tolerance frame.

Also known as: Straightness callout

Engineering & technicalStandard profile

Meanings

A plain horizontal line in a tolerance frame limits how much a line element or an axis may deviate from straight. It is a form tolerance, so it needs no datum: straightness is a property of the feature itself.

Officially standardisedVerified fact
Limits deviation of a line element or an axis from a perfectly straight line.
Contexts: Technical drawing
Officially standardisedVerified fact
Is a tolerance of form and therefore requires no datum, unlike orientation and location tolerances which are always measured against one.
Contexts: Technical drawing

Visual description

A single horizontal line drawn in the left compartment of a rectangular frame.

Symmetry: none
Orientation: upright

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

ISO 1101, Geometrical product specifications — Geometrical tolerancing
International Organization for Standardization · retrieved 2026-08-01
Paywalled and NOT READ. Registered so records can state which standard governs a symbol — a checkable fact a reader can act on — and for nothing else. It governs the geometric tolerancing symbols and their frames. No meaning in any record is typed `official` on the strength of this entry. See docs/paywalled-standards.md.
Geometric dimensioning and tolerancing
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol instructs and which standard governs it. Where a standard is named it is reported by this source rather than read, so no meaning is typed `official` on that basis.
ASME Y14.5, Dimensioning and Tolerancing
American Society of Mechanical Engineers · retrieved 2026-08-01
Paywalled and NOT READ. Registered so records can state which standard governs a symbol — a checkable fact a reader can act on — and for nothing else. It is the American counterpart to ISO 1101 and differs from it in detail. No meaning in any record is typed `official` on the strength of this entry. See docs/paywalled-standards.md.

Last reviewed 2026-08-23

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Engineering drawing notation

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Meanings

Officially standardisedVerified fact

Limits deviation of a line element or an axis from a perfectly straight line.

Contexts: Technical drawing

Officially standardisedVerified fact

Is a tolerance of form and therefore requires no datum, unlike orientation and location tolerances which are always measured against one.

Contexts: Technical drawing

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

ISO 1101, Geometrical product specifications — Geometrical tolerancing
International Organization for Standardization · retrieved 2026-08-01
Paywalled and NOT READ. Registered so records can state which standard governs a symbol — a checkable fact a reader can act on — and for nothing else. It governs the geometric tolerancing symbols and their frames. No meaning in any record is typed `official` on the strength of this entry. See docs/paywalled-standards.md.
Geometric dimensioning and tolerancing
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol instructs and which standard governs it. Where a standard is named it is reported by this source rather than read, so no meaning is typed `official` on that basis.
ASME Y14.5, Dimensioning and Tolerancing
American Society of Mechanical Engineers · retrieved 2026-08-01
Paywalled and NOT READ. Registered so records can state which standard governs a symbol — a checkable fact a reader can act on — and for nothing else. It is the American counterpart to ISO 1101 and differs from it in detail. No meaning in any record is typed `official` on the strength of this entry. See docs/paywalled-standards.md.

Last reviewed 2026-08-23