What this module covers
A welding symbol is the drawing's instruction to the welder and the inspector: what weld, where, how big, how long, and how it is to be finished and examined. An NDE symbol does the same for examination. Both follow the system laid out in AWS A2.4. Misread one and you inspect the wrong weld to the wrong size.
Under AWS B5.1:2025 Table 8.1, Symbols carries a minimum weight of 10% of Part A. Part A is closed book (165 questions, 150 scored, in 135 minutes at Prometric), so you need the placement rules memorized. Practice by sketching symbols from a description, then describing symbols back in words.
We explain the system in our own words. Keep your own copy of AWS A2.4 for the full set of figures.
Where each element of a welding symbol sits
The parts
| Element | Required? | What it does |
|---|---|---|
| Reference line | Always | The horizontal line everything else hangs from |
| Arrow | Always | Points to the joint the symbol is about |
| Tail | Only when needed | Holds a process, specification or other note |
| Weld symbol | Usually | The small shape that names the weld type (fillet, groove, plug and so on) |
| Dimensions | When needed | Size, length, pitch, root opening, angle |
| Supplementary symbols | When needed | Weld all around, field weld, contour, backing and similar |
The welding symbol is the whole assembly. The weld symbol is just the small shape on the line. Keep the two terms apart.
Arrow side and other side
The arrow touches one side of the joint. That side is the arrow side, and the opposite side is the other side.
- A weld symbol below the reference line means weld on the arrow side.
- A weld symbol above the reference line means weld on the other side.
- Symbols on both sides mean weld both sides.
This holds whichever way the arrow points.
The arrow break
For a bevel or J groove, only one member is prepared. If the arrow has a break (a bend) in it, the break points toward the member that gets the bevel or J. If it is not broken, the choice of member is left open.
Tail and multiple reference lines
The tail is the V shaped fork at the end of the reference line, left off when there is nothing to say. It can carry a process (for example, SMAW), a WPS number or another reference.
When several operations are needed on one joint, the symbol can stack several reference lines on one arrow. The line nearest the arrow is the first operation, and the others follow in order outwards.
What the exam tests here
Arrow side versus other side, what the tail is for, and the order of operations on stacked reference lines.
Weld symbols, dimensions and supplementary symbols
Fillet welds
Dimensions read from left to right along the reference line, on the same side as the symbol.
- Left of the symbol: the fillet size (leg).
- Right of the symbol: the length, then a hyphen, then the pitch for intermittent welds.
- No length means the weld runs the full length of the joint (or between abrupt changes in direction).
Example (invented values): a 6 mm fillet with 50-150 to the right means 50 mm segments spaced 150 mm center to center. Pitch is always measured center to center, not from the end of one segment to the start of the next.
Chain intermittent welds have segments directly opposite each other on both sides. Staggered intermittent welds have the symbols offset on the two sides of the reference line, and the segments alternate along the joint.
Groove welds
Groove symbols (square, V, bevel, U, J, flare V and flare bevel) can carry more information than a fillet.
| Where | What it shows |
|---|---|
| Left of the symbol | Depth of groove preparation, then the groove weld size in parentheses |
| Inside the symbol | Root opening |
| Beyond the root opening (further from the line) | Groove angle |
| Right of the symbol | Length, when the groove weld is not full length |
Two depths cause the most confusion. The depth of preparation is how deep the joint was beveled or grooved. In the parentheses you read the groove weld size: how much joint penetration the weld must provide. That can be more than the preparation depth when the weld penetrates past it. On a complete joint penetration groove with no size shown, the weld is intended to go through the full thickness.
Other weld symbols
Recognize plug, slot, spot, seam, stud, surfacing, edge and back or backing weld symbols by shape. For plug and slot welds, a depth of filling is written inside the symbol when the hole is not filled completely.
Supplementary symbols
- Weld all around: a small circle where the arrow meets the reference line. Weld the whole way round the joint.
- Field weld: a flag at the same junction. The weld is made on site, not in the shop.
- Melt through: a filled shape on the opposite side, showing visible root reinforcement is required.
- Backing and spacer: a small rectangle, often with a note in the tail on material and whether the backing stays.
- Consumable insert: a square symbol on the side opposite the groove.
- Contour: a line over the weld symbol, flush (straight), convex (bulging) or concave (dished).
A contour symbol can carry a finishing letter that tells you how the contour is reached:
| Letter | Method |
|---|---|
| C | Chipping |
| G | Grinding |
| H | Hammering |
| M | Machining |
| R | Rolling |
| U | Unspecified |
What the exam tests here
Reading a fillet or groove dimension in the right position, the difference between chain and staggered intermittent welds, and naming supplementary symbols.
Examination symbols
Same frame, different content
An NDE symbol uses the same reference line, arrow and tail. In place of a weld symbol, it carries the letters of the examination method.
| Letters | Method |
|---|---|
| VT | Visual |
| PT | Liquid penetrant |
| MT | Magnetic particle |
| RT | Radiographic |
| UT | Ultrasonic |
| ET | Electromagnetic (eddy current) |
| AET | Acoustic emission |
| LT | Leak |
| PRT | Proof |
| NRT | Neutron radiographic |
Placement
- Letters below the line: examine the arrow side.
- Letters above the line: examine the other side.
- Letters centered on the line: no side is specified, so the location does not depend on side.
Several methods can be shown together, for example PT and UT on the same line, joined with a plus sign.
Extent and other details
- A length to the right of the letters limits the examination to that length. No length means the full length.
- A number in parentheses above or below the letters gives the number of examinations, used for spot or partial examination.
- The examine all around circle and the field examination flag work just as they do on a welding symbol.
- For radiography, a separate arrow with an angle can show the direction of radiation.
Combined symbols
Welding and examination information can share one reference line or be stacked on several. The usual reading still applies.
What the exam tests here
Naming a method from its letters, reading which side is examined, and spotting what a centered letter group means.
Check yourself
The three questions below cover the arrow side and other side rule, reading an intermittent fillet weld dimension, and what centered examination letters mean.
Where to look in your own books
- AWS A2.4:2020: welding symbols, the elements and their positions, arrow side and other side, dimensions, supplementary symbols and finishing letters
- AWS A2.4:2020: examination symbols, method letters and extent of examination
- AWS A3.0M/A3.0:2020: names of joint types and weld types the symbols refer to
- AWS Welding Inspection Technology: the chapter on welding and NDE symbols
- AWS B1.10M/B1.10: NDE methods named by the examination letters
- AWS B5.1:2025: Part A body of knowledge and Table 8.1 weights