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AWS Welding Symbols Reference (A2.4 Chart)

A welding symbol packs the whole joint instruction into a few lines and shapes. This searchable chart explains each element of an AWS A2.4 symbol, where it sits and the mistakes that cause shops to weld the wrong side.

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Symbol element	Meaning	Where it sits	Reading note
Reference line	Horizontal line that carries all weld information	Center of the whole symbol	Always read from the reference line outward
Arrow	Points to the joint or member to be welded	Attached to one end of the reference line	Defines which side is the arrow side
Arrow side	The side of the joint the arrow touches	Weld symbol BELOW the reference line	Most common beginner mix-up
Other side	The side of the joint opposite the arrow	Weld symbol ABOVE the reference line	Symbols on both sides mean welds on both sides
Tail	Carries process, specification, procedure or note	Fork at the end of the reference line opposite the arrow	Omitted when no notes are needed
Fillet weld symbol	Fillet weld (triangle)	Triangle with its vertical leg always on the left	Leg size is written on the left of the triangle
Square groove symbol	Square groove weld (two parallel lines)	On the reference line	Root opening is written inside the symbol
V groove symbol	Single V groove weld	On the reference line	Groove angle goes in the symbol, root opening inside
Bevel groove symbol	Single bevel groove weld	Vertical leg on the left, slanted leg on the right	The arrow bends toward the member to be beveled
U groove symbol	Single U groove weld	On the reference line	Radius and root face noted by dimensions
J groove symbol	Single J groove weld	On the reference line	Arrow bends toward the grooved member
Flare V groove symbol	Flare V groove weld	On the reference line	Used for rounded members such as tube or bar
Plug or slot symbol	Plug or slot weld (rectangle)	On the reference line	Hole or slot size and pitch are dimensioned
Spot weld symbol	Spot weld (circle)	On or astride the reference line	Diameter on the left, spacing on the right
Seam weld symbol	Seam weld (circle with two parallel lines)	On or astride the reference line	Width on the left, length on the right
Back or backing symbol	Back weld or backing (arc shape)	Opposite side from the groove weld symbol	Back weld is made after the groove weld
Surfacing symbol	Surfacing (overlay) weld	Below the reference line for arrow side	Size gives the minimum overlay height
Melt-through symbol	Root penetration visible on the far side	Opposite the groove symbol, filled shape	Height of reinforcement may be dimensioned
Weld all around	Weld continues around the whole joint	Circle at the junction of arrow and reference line	Joint must be fully continuous or sequential
Field weld	Weld made at the installation site, not in the shop	Solid flag at the junction of arrow and reference line	Flag usually points toward the tail
Contour: flush	Finish weld flush with the surface	Flat line over the weld symbol	Add a finish letter for the method
Contour: convex	Finish weld with convex face	Convex arc over the weld symbol	Default for most fillet welds
Contour: concave	Finish weld with concave face	Concave arc over the weld symbol	Often specified for fatigue-loaded fillets
Finish letters	C chipping, G grinding, H hammering, M machining, P peening, R rolling	Next to the contour mark	Indicates the method, not the surface roughness
Length and pitch	Intermittent weld: length then center-to-center pitch	Right of the weld symbol, such as 2-5	2-5 means 2 long segments every 5 center to center
Dimension left of symbol	Size: fillet leg or groove depth	Left of the weld symbol	Applies to the side where the symbol sits

Based on the structure of AWS A2.4. ISO 2553 uses a dual reference line (solid plus dashed) and different placement rules, so check which standard the drawing cites.

Link weld procedures to your routings

Optional: a short review of how to attach WPS and welder qualification data to ERP routings.

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How to use this chart

Type a term such as fillet, field weld or arrow side into the search box to filter the rows. Read the Where it sits column first, because position carries most of the meaning in a welding symbol. The same triangle means a different weld depending on whether it is above or below the reference line. Export the filtered or full table to Excel or PDF for a shop-floor poster or a training handout.

The standard behind it

AWS A2.4 defines the symbols for welding, brazing and nondestructive examination used on North American drawings. The reference line, arrow and tail form the skeleton, and basic weld symbols, supplementary symbols and dimensions hang from it in fixed positions. Dimensions to the left of a symbol are sizes, and dimensions to the right are lengths and pitches. ISO 2553 is the international equivalent and differs in the dashed identification line, so never mix the two without checking the drawing note.

Common reading mistakes

Most rework traces back to a small set of misreadings that this table lets you check in seconds.

Swapping arrow side and other side: below the line is the arrow side.
Reading the fillet triangle backwards: the vertical leg is always on the left.
Ignoring the tail, which may carry the WPS number or process.
Treating 2-5 as a size instead of length and pitch.
Missing the field weld flag on a shop drawing.

Frequently Asked Questions

Which side is the arrow side in a welding symbol?

The arrow side is the side of the joint the arrow touches. The weld symbol is placed below the reference line for the arrow side and above the line for the other side. If symbols appear on both sides, weld both sides.

What does a circle at the arrow bend mean?

A circle where the arrow meets the reference line means weld all around. The weld continues around the full joint, which may include several members. It does not apply to partial joints, so give the length explicitly there.

What is the difference between AWS and ISO welding symbols?

AWS A2.4 uses a single reference line and places the arrow side symbol below it. ISO 2553 uses a solid line plus a dashed identification line, and the arrow side symbol sits on the solid line side. Always check which standard the drawing cites.

Does the symbol tell me which welding process to use?

Only if a process abbreviation or WPS number is placed in the tail. If the tail is empty, the process comes from the contract, the applicable code or the shop procedure. Add the WPS reference to the tail to remove ambiguity.

If drawings and WPS numbers live in your ERP or PLM, Netray can help you link weld symbols and procedures to routings so shops see the right instruction at the work center.

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