Weld symbol
Multiple reference lines
Stacked reference lines on one arrow spell out a sequence of operations. The line nearest the arrow is done first, and each line further out is done after the one before it.
Reads asArrow side: bevel-groove weld, 1/2 size, 45° groove angle, 1/4 root opening. Other side: back weld.
How to read it
Most symbols carry one reference line. When a joint needs several operations performed in a defined order, the drawing can stack additional lines above the first, all sharing the same leader and arrow. Each line holds a complete instruction of its own, with its own weld symbols, dimensions, supplementaries, and tail.
Order is read outward from the arrow. The line closest to the arrow is the first operation, the next line out is the second, and so on. That is the one thing multiple reference lines add that a single line cannot express: a single line says what to do but never in what order, while stacked lines say exactly that.
The arrangement earns its complexity on joints where a step in the middle changes what follows - gouge the root, then weld, then examine, then dress. Each of those can occupy its own line, with a note or process reference in its own tail, so the whole sequence sits on one symbol instead of being scattered across a page of notes.
The rest of the notation carries over unchanged. Each line has its own arrow side and other side, its own elbow supplementaries, and its own tail, and the shared arrow means every line refers to the same joint. Read them one at a time from the arrow outward rather than trying to take the whole stack in at once, and the arrangement stops looking intimidating.
Where each dimension goes
- Line nearest the arrow
- The first operation in the sequence.
- Each successive line outward
- The next operation, performed after everything on the lines closer to the arrow.
- Per-line tails
- Each line can carry its own process, procedure, or note applying to that step alone.
- Shared arrow
- Every stacked line refers to the same joint, so the stack is a sequence rather than a list of separate welds.
- Per-line supplementaries
- All-around circles and field flags belong to their own line's elbow and govern only that step.
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: Weld, back gouge, then back weld
TitleWeld, back gouge, then back weldRefMultiple reference linesEx1 / 2Reads as
Fill the bevel first, then gouge and back weld the far side as the next step.
Which mark says so
- bevel-groove symbolBelow the reference lineA bevel-groove weld on the arrow side of the joint
- 1/2Left of the arrow-side symbolGroove weld size - how deep the weld itself goes
- 45°Beyond the outer face of the arrow-side symbolIncluded angle the joint is prepared to
- 1/4Inside the arrow-side symbolRoot opening - the gap left between the members before welding
- back symbolAbove the reference lineA back weld on the far side of the joint
- Broken leaderOn the arrow itselfThe arrow points at the member to be prepared
- Back gouge before back weldIn the tailA reference the drawing carries - a process, procedure or specification
Stacked lines put the groove on the line nearest the arrow and the back-side work on the line above it, so the order is stated rather than left to the fabricator.
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.
Example 2: Shop weld first, field weld second
TitleShop weld first, field weld secondRefMultiple reference linesEx2 / 2Reads as
Make the shop fillet first and leave the flagged weld for site erection.
Which mark says so
- fillet symbolBelow the reference lineA fillet weld on the arrow side of the joint
- 5/16Left of the arrow-side symbolLeg size of the fillet
- fillet symbolAbove the reference lineA fillet weld on the far side of the joint
- 5/16Left of the other-side symbolLeg size of the fillet
- Flag at the elbowWhere the leader meets the reference lineField weld - made on site rather than in the shop
- Field weld secondIn the tailA reference the drawing carries - a process, procedure or specification
One line carries the shop weld and a line further from the arrow carries the flagged field weld, so the field flag governs only its own step rather than the whole symbol.
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
- Reading the stack from the top down instead of outward from the arrow.
- Treating each stacked line as a separate joint when they all share one arrow and one joint.
- Applying a supplementary symbol from one line to the whole stack.
- Ignoring the sequence entirely and welding in whatever order is convenient.