Centre line

A long-dash-dot line marking an axis of symmetry or a circle's centre.

Also known as: Center line, Axis line, Dash dot line

Engineering & technicalStandard profile

Meanings

A line of alternating long dashes and dots is a centre line: it marks an axis rather than an edge. Line style is a vocabulary in technical drawing, and reading a centre line as a physical edge is the commonest beginner's error.

Common modern usageVerified fact
Marks an axis of symmetry, the centre of a circle or the path of a moving part — never a physical edge of the object.
Contexts: Technical drawing
Common modern usageVerified fact
Belongs to a vocabulary of line styles in which the pattern carries the meaning: continuous for visible edges, dashed for hidden ones, dash-dot for axes.
Contexts: Technical drawing
Common modern usageVerified fact
Crosses at the centre of a circle so the intersection marks the exact point, which is why holes are dimensioned from it.
Contexts: Technical drawing

Visual description

A thin line made of long dashes separated by single short dashes or dots, repeating evenly along its length.

Symmetry: point
Orientation: orientation independent

Commonly confused with: Hidden line
Both are broken thin lines; the dash-dot rhythm against even dashes is the whole distinction.
Part of the same system as: Hidden line
Members of the line-type vocabulary where the pattern is the meaning.

Compare: Centre line vs hidden line →

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

Engineering drawing
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.
ISO 128, Technical drawings — General principles of presentation
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 line types, views, sections and projection conventions. No meaning in any record is typed `official` on the strength of this entry. See docs/paywalled-standards.md.
Technical drawing
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.

Last reviewed 2026-07-31

Part of

Technical drawing notation

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Meanings

Common modern usageVerified fact

Marks an axis of symmetry, the centre of a circle or the path of a moving part — never a physical edge of the object.

Contexts: Technical drawing

Common modern usageVerified fact

Belongs to a vocabulary of line styles in which the pattern carries the meaning: continuous for visible edges, dashed for hidden ones, dash-dot for axes.

Contexts: Technical drawing

Common modern usageVerified fact

Crosses at the centre of a circle so the intersection marks the exact point, which is why holes are dimensioned from it.

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

Engineering drawing
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.
ISO 128, Technical drawings — General principles of presentation
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 line types, views, sections and projection conventions. No meaning in any record is typed `official` on the strength of this entry. See docs/paywalled-standards.md.
Technical drawing
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.

Last reviewed 2026-07-31

Meanings

Visual description

Related & commonly confused symbols

Meanings

Visual description

Related & commonly confused symbols