The rule is fixed: below the reference line = arrow side. Above = other side. Not all weld types have side significance — stud and surfacing welds are arrow-side only.
Direct Answer
Arrow side = the side of the joint the arrow points toward. Weld symbols placed below the reference line apply to the arrow side (A2.4 §6.2.1). Weld symbols placed above the reference line apply to the other side (§6.2.2). A symbol on both sides of the reference line means weld both sides (§6.2.3). The terms "arrow side" and "other side" are the official AWS A2.4 terminology.
AWS A2.4:2020 §6.2.1–§6.2.3
The Rule — Below and Above the Reference Line
The reference line is the horizontal line that is the backbone of every welding symbol. Where the weld symbol sits relative to that line determines which side of the joint gets welded.
Position
Side
A2.4 Citation
Below the reference line
Arrow Side
§6.2.1
Above the reference line
Other Side
§6.2.2
Both sides of the reference line
Arrow + Other
§6.2.3
Key Distinction
"Arrow side" does not mean the left side, right side, top, or bottom of a drawing. It means the physical side of the joint where the arrow makes contact. The same symbol can apply to the top, bottom, or either face of a joint depending on how the arrow is drawn.
AWS A2.4:2020 §6.1.1–§6.1.4
Side Significance by Weld Type
Not all weld types use arrow side and other side the same way. A2.4 §6.1 divides weld symbols into four categories.
Weld Types
Side Rule
Citation
Fillet, groove, edge welds
Arrow contacts the outer surface of one joint member. That member's side = arrow side.
§6.1.1
Plug, slot, spot, projection, seam welds
Arrow contacts the outer surface of one member at the centerline of the desired weld. The member the arrow points toward = arrow-side member.
§6.1.2
Resistance spot (RSW), resistance seam (RSEW)
No Side Significance
§6.1.3 + §11.1.1.3, §12.1.1.3
Stud welds, surfacing welds
Arrow Side Only — applied on a surface, not at a joint
§6.1.4
For RSW and RSEW: §6.1.3 states that some weld symbols have no arrow-side or other-side significance. The process-specific confirmation for resistance spot welds appears in §11.1.1.3, and for resistance seam welds in §12.1.1.3. Supplementary symbols used alongside these may still have side significance.
More Questions
Arrow Side and Other Side FAQ
What is the arrow side of a weld symbol?
The arrow side is the side of the joint that the arrow points toward. Per AWS A2.4 §6.2.1, weld symbols placed below the reference line apply to the arrow side of the joint. The arrow contacts the outer surface of one joint member — that member's side is the arrow side. The term does not refer to absolute position on the drawing; it refers to the physical side of the joint at the arrow location.
What is the other side of a weld symbol?
The other side is the side of the joint opposite to where the arrow points. Per A2.4 §6.2.2, weld symbols placed above the reference line apply to the other side. A weld symbol on both sides of the reference line means weld both sides of the joint, per §6.2.3.
Which weld symbols have no arrow side or other side significance?
Per A2.4 §6.1.3, some weld symbols have no arrow-side or other-side significance. For resistance spot welds (RSW) and resistance seam welds (RSEW), this is confirmed in §11.1.1.3 and §12.1.1.3 respectively. Per §6.1.4, stud welds and surfacing welds are arrow-side only — they are applied on a surface rather than at a joint and are never shown as other-side welds.
What is the most common mistake with arrow side and other side?
The most common mistake is reversing above and below — placing a symbol above the line thinking it means arrow side. The rule is always: below = arrow side, above = other side, per A2.4 §6.2.1 and §6.2.2. A second common mistake is welding only the arrow side when a symbol appears on both sides of the reference line, which means both sides must be welded per §6.2.3.