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Edge weld symbol: what it means on a drawing

Fillet Gauge editorial teamSources checked 4 min read

The edge weld symbol is three parallel strokes joined at their outer ends, standing on the reference line. It calls for a weld across the edges of two or more members laid together, most often sheet metal or other thin gauge material. The size on its left is the depth of fusion, measured down from the edges.

Two thin sheets standing face to face, drawn end on, with a weld bead across their top edges, beside an edge weld symbol with 1/16 on its left and nothing on its right
Three joined strokes. Size on the left, and no length means full length. Numbers are invented.
Use this diagram

How to read it

  1. Find the side. Below the line, the edge weld goes on the arrow side. Above the line, the other side. An edge joint between flat members can be welded on both sides, and then the mark appears on both sides of the line.
  2. Read the left side. The number is the weld size: how deep the weld fuses into the edges. It isn't the width of the bead, though the two can come out about the same. With no size, the welder chooses.
  3. Read the right side. A single number is the length. Length and pitch, such as 1-4, make the edge weld intermittent, chain or staggered just like a stitch fillet. No number means the weld runs the full length of the edge.
  4. Count the members. One arrow and one edge weld symbol can cover an edge joint made of three or more sheets stacked together.
  5. Look opposite. A filled half-circle opposite an edge weld asks for melt-through, weld metal showing through on the far side, which is common on flanged sheet joints.

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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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Which joints take an edge weld

Edge joints, where two sheets lie face to face and the weld runs along their shared edge. Flanged butt joints, where both edges are turned up and the flanges are welded together. Flanged corner joints, where one or both members are bent at the corner. The other side of a flanged joint is often a flare shape, which is why edge welds and flare-V welds turn up on the same sheet-metal drawings.

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Common mix-ups

  • Edge weld or square groove. The square groove is two separate parallel strokes. The edge weld has three strokes joined at their ends. Count before you read.
  • Edge weld or plug weld. The edge mark has a middle stroke between its two outer strokes. The plug and slot rectangle is a plain box with no middle stroke.
  • Size or width. The number on the left is depth of fusion. Measuring the bead across its face doesn't check it.
  • Melt-through or back weld. On an edge weld, a filled half-circle is melt-through, not a separate bead.

Edge welds on the CWI exam

Edge marks are part of Symbols, Welding and NDE, at least 10% of CWI Part A, a closed-book part, and they are easy to confuse with the square groove when you rush. Part B drawings fall under Utilization of Specifications and Drawings, at least 8% of the practical.

Practice it

The welding symbols quiz includes the edge weld mark among the groove and plug shapes and explains each answer. See it beside every other basic shape on the welding symbols chart.

Three strokes sorted? Check the rest of Part A

Take the free 10-question check. It's weighted to the Part A outline, scored by domain and needs no signup, so you see whether symbols or another domain costs you the most points. The Part A course gives you a lesson on reading welding and NDE symbols and on every other exam subject, two full-length timed practice exams, and a worked explanation with every answer.

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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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