Arrow side or other side?

Look at the symbol and decide where the weld goes. Get 10 right to finish the lesson. Pick AWS or ISO in the box below.

How to read it

Every welding symbol has a reference line and an arrow. The arrow points at the joint. The side of the joint it touches is the arrow side. The opposite side is the other side. Where the weld symbol sits on the reference line tells you which side to weld.

AWS A2.4 (US)

Below the line means arrow side. Above the line means other side. A symbol on both sides means weld both sides.

ISO 2553 System A (Europe)

System A uses two lines: a solid reference line and a dashed line next to it. A symbol on the solid line means arrow side. A symbol on the dashed line means other side. When the weld is on both sides, the dashed line is left out.

The dashed line can also be drawn above the solid line. The rule stays the same: what touches the solid line is the arrow side.

ISO 2553 System B

System B uses one reference line, read the same way as AWS: below the line is the arrow side, above is the other side. A drawing should say which system it uses, often in the title block or the welding notes.

Common mistakes

• Reading an ISO System A drawing as if it were AWS. Find the dashed line first.
• Thinking the arrow pointing left or right changes the side. It does not.
• Missing a second symbol on the other side of the line, which means both sides get welded.

Questions

Does it matter which way the arrow points?

No. The arrow can leave from either end of the reference line. You read the side from where the symbol sits, not from the direction of the arrow.

What exactly is the arrow side?

The arrow side is the side of the joint the arrow touches. The other side is the opposite side of the same joint.

Why is there a dashed line on ISO welding symbols?

In ISO 2553 System A, the dashed line marks the other side. A symbol on the solid line means the arrow side, a symbol on the dashed line means the other side. The dashed line can be drawn above or below the solid line.

Do AWS and ISO 2553 System B read the same?

For arrow side and other side, yes: below the line is the arrow side, above is the other side. They still differ in other details, such as how fillet sizes and intermittent welds are written.

Explained in our own words. For the full rules, see AWS A2.4:2020 and ISO 2553:2019.