Weld symbol
Weld symbol tail and specification reference
The forked tail at the far end of the reference line holds information the symbol itself cannot carry: the process, the procedure, the consumable, or a note the joint depends on.
Reads asArrow side: V-groove weld, 1/2 size, 60° groove angle, 1/8 root opening.
How to read it
The tail is drawn as a two-pronged fork at the end of the reference line opposite the arrow. It exists because the geometry of a symbol can only express geometry. Anything else the joint depends on - which process to use, which procedure governs it, which consumable, which inspection requirement - has to be written out, and the tail is where that text lives.
Process abbreviations are the most common content. Naming the process in the tail matters because the same joint geometry behaves very differently depending on how it is welded: a groove that a wire process fills easily may be impractical with a covered electrode, and a root that one process reaches cleanly another will bridge. Reading the tail before planning the weld saves rework.
Procedure and specification references are the next most common. A short code in the tail points to a written document that carries preheat, interpass temperature, technique, and consumable requirements far beyond anything a symbol could show. When you see one, the symbol is telling you it is not the whole instruction and the referenced document is part of the drawing.
A tail can also carry a plain note - a penetration requirement, an inspection method, a sequence instruction. And a reference line with no tail at all is complete on its own: the absence of a tail means no additional reference applies, not that something has been left off. Learning to read that absence as information rather than omission is part of reading symbols fluently.
Where each dimension goes
- Tail position
- A forked shape at the end of the reference line opposite the arrow, so it reads as a footnote to the whole symbol.
- Process abbreviation
- Names how the joint is to be welded, which affects what preparation and root treatment are practical.
- Procedure or specification reference
- Points to a written document carrying preheat, technique, and consumable requirements the symbol cannot show.
- Plain notes
- Penetration requirements, inspection methods, or sequence instructions written out where no symbol exists for them.
- No tail
- Means no additional reference applies. Absence is information, not an omission.
Worked examples
Each one is a drawing, the sentence it comes out as, and then the mark-by-mark account of why. Read the sheet first and say the sentence yourself before you look down.
Example 1: Process and procedure in the tail
TitleProcess and procedure in the tailRefThe tailEx1 / 2Reads as
Weld this groove by the named process, following the referenced procedure.
Which mark says so
- V-groove symbolBelow the reference lineA V-groove weld on the arrow side of the joint
- 5/8Left of the symbolGroove weld size - how deep the weld itself goes
- 60°Beyond the outer face of the symbolIncluded angle the joint is prepared to
- 1/8Inside the symbolRoot opening - the gap left between the members before welding
- FCAW / WPS-07In the tailA reference the drawing carries - a process, procedure or specification
The tail carries both a process abbreviation and a procedure code, which together define preheat, technique, and consumable well beyond anything the symbol's geometry could show.
And what it does not say
- No length is given, so each weld runs the full length of the joint.
- Nothing sits above the reference line, so the far face of the joint stays bare.
- There is no circle at the elbow, so the weld does not continue around the joint.
Example 2: Inspection requirement in the tail
TitleInspection requirement in the tailRefThe tailEx2 / 2Reads as
Weld the fillets both sides and examine them by the method the tail names.
Which mark says so
- fillet symbolBelow the reference lineA fillet weld on the arrow side of the joint
- 3/8Left of the arrow-side symbolLeg size of the fillet
- fillet symbolAbove the reference lineA fillet weld on the far side of the joint
- 3/8Left of the other-side symbolLeg size of the fillet
- Magnetic particle examineIn the tailA reference the drawing carries - a process, procedure or specification
The tail carries an inspection instruction rather than a process, which is a legitimate use: it holds any requirement the joint depends on that has no symbol of its own.
And what it does not say
- No length is given, so each weld runs the full length of the joint.
- There is no circle at the elbow, so the weld does not continue around the joint.
Common mistakes
- Ignoring a procedure reference in the tail and welding to the symbol's geometry alone.
- Reading a missing tail as an incomplete symbol rather than as a statement that nothing further applies.
- Putting dimensional information in the tail that belongs beside the weld symbol.
- Assuming the tail's process abbreviation is advisory when it is part of the instruction.