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Spot weld symbol: what it means on a drawing

Fillet Gauge editorial teamSources checked 3 min read

The spot weld symbol is a circle on the reference line. It calls for spot welds: small, roughly round welds that join overlapping members at separate points, most often made by resistance welding between two sheets. A circle centered on the line has no arrow side or other side, because the weld forms between the members.

A spot weld symbol centered on the reference line with 1/4 on its left, 2 on its right and RSW in the tail, above a top view of two overlapping sheets joined by a row of spot welds, and a section of the nugget between the sheets
Centered on the line: the weld forms between the sheets. Numbers are invented.
Use this diagram

How to read it

  1. Check the position. Centered on the line means no side significance. Some spot welds, such as arc spot welds made through one sheet, are drawn on one side of the line instead, and then the side matters the way it does for other welds.
  2. Read the left side. The number on the left is the spot size, the weld diameter. Older drawings sometimes put a shear strength there, but under A2.4:2020 the left number is size only. A required strength goes in a note in the tail.
  3. Read the right side. The number on the right is the pitch, the center-to-center spacing of the spots.
  4. Look for a number in parentheses. A number in parentheses with the symbol gives how many spot welds to make.
  5. Read the tail. The process goes there. RSW is resistance spot welding, the most common way spot welds are made.

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Symbols - Welding and NDE

On a welding symbol, what does a circle at the junction of the arrow and the reference line indicate?

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Common mix-ups

  • Spot circle or all-around circle. The weld all around circle sits at the bend where the arrow meets the reference line, alongside another weld symbol. The spot circle sits on the line in the weld symbol's place and is the weld symbol.
  • Spot or seam. A seam weld symbol is the same circle crossed by two parallel lines. A seam is a continuous weld along the overlap, often made with rotating wheel electrodes, rather than separate points.
  • Spot or stud. The stud weld mark is a circle with an X inside it, for welding a stud or pin to a surface.
  • Spot or plug. A plug weld fills a hole in one member and uses a rectangle. A spot weld needs no hole.

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On the CWI exam

Spot, seam and stud marks belong to Symbols, Welding and NDE, at least 10% of CWI Part A, read from memory because Part A is closed book. They appear less often on structural drawings than fillets and grooves, so they're worth a few minutes of extra drilling. Part B drawings fall under Utilization of Specifications and Drawings, at least 8% of the practical exam.

Practice it

The welding symbols quiz mixes spot and seam marks in with the groove and fillet shapes and explains each answer. Build a centered spot weld in the welding symbol builder, then see the circle beside every other basic shape on the welding symbols chart.

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Facts checked 24 October 2026 against the sources listed above. If something has changed, tell us and we will correct it within 2 business days.

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