Hidden line

A line of short even dashes, showing an edge concealed behind material.

Also known as: Dashed line drawing, Invisible edge line

Engineering & technicalStandard profile

Meanings

Short even dashes show an edge that exists but cannot be seen from this view. It is the drawing's way of being honest about what is behind the surface without cutting the object open.

Common modern usageVerified fact
Shows an edge or surface that is present but concealed from this viewing direction by material in front of it.
Contexts: Technical drawing
Common modern usageVerified fact
Is omitted where a section view is drawn instead, since cutting the object open makes the concealed feature a visible edge.
Contexts: Technical drawing

Visual description

A thin line of short dashes of even length separated by even gaps, running the length of the concealed edge.

Symmetry: point
Orientation: orientation independent

Commonly confused with: Centre line
Both are broken lines; the dash-dot rhythm is the whole distinction.
Part of the same system as: Centre line
The line-type vocabulary.

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

Short even dashes show an edge that exists but cannot be seen from this view. It is the drawing's way of being honest about what is behind the surface without cutting the object open.

Common modern usageVerified fact

Shows an edge or surface that is present but concealed from this viewing direction by material in front of it.

Contexts: Technical drawing

Common modern usageVerified fact

Is omitted where a section view is drawn instead, since cutting the object open makes the concealed feature a visible edge.

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