Welding symbol

An arrow and horizontal reference line carrying weld type, size and process.

Also known as: Weld symbol, Arrow with a flag drawing, Line with a triangle

Engineering & technicalStandard profile

Meanings

A welding symbol is a small notation system rather than one mark. Which side of the reference line the weld symbol sits on states which side of the joint is welded — and the two standards disagree about that, which is a genuine hazard.

Common modern usageVerified fact
Specifies a weld's type, size, length and process on a single arrow-and-reference-line assembly pointing at the joint.
Contexts: Technical drawing
Common modern usageVerified fact
States which side of the joint is welded by which side of the reference line the weld symbol sits on — below for the arrow side, above for the other.
Contexts: Technical drawing
Common modern usageVerified fact
Follows conventions that differ between the ISO and American systems, so the same drawing can be read two ways. Which standard governs a drawing is stated in its title block for exactly this reason.
Contexts: Technical drawing

Visual description

A leader arrow pointing at a joint, meeting a horizontal reference line that carries a small geometric symbol above or below it, with figures written to either side.

Symmetry: none
Orientation: orientation independent

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 2553, Welding and allied processes — Symbolic representation on drawings
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 welding symbols, their arrow and reference line construction. No meaning in any record is typed `official` on the strength of this entry. See docs/paywalled-standards.md.
Welding symbol
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.
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

Specifies a weld's type, size, length and process on a single arrow-and-reference-line assembly pointing at the joint.

Contexts: Technical drawing

Common modern usageVerified fact

States which side of the joint is welded by which side of the reference line the weld symbol sits on — below for the arrow side, above for the other.

Contexts: Technical drawing

Common modern usageVerified fact

Follows conventions that differ between the ISO and American systems, so the same drawing can be read two ways. Which standard governs a drawing is stated in its title block for exactly this reason.

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 2553, Welding and allied processes — Symbolic representation on drawings
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 welding symbols, their arrow and reference line construction. No meaning in any record is typed `official` on the strength of this entry. See docs/paywalled-standards.md.
Welding symbol
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.
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