Back or backing weld
A filled half circle on the reference line: a back or backing weld, a bead deposited at the back of a single groove weld.
How to read it
A back weld is deposited at the back of a single groove weld, and a backing weld is backing in the form of a weld. The symbol is placed on the side of the reference line opposite the groove weld symbol it goes with. Dimensions of back or backing welds are not shown on the welding symbol.
This explains what a symbol specifies on a drawing. It isn't welding instruction, and a drawing's own notes and the governing code take precedence.
Differences by country or standard
India's IS 813:1986, which draws on ISO 2553, lists the same weld as a backing run, back or backing weld.
Read next
- Next in Welding symbolsSurfacing weldTwo small arcs on the reference line: a surfacing weld, a layer of weld metal deposited on a surface.
- The same shape in BPMN symbolsSequence flow and message flowThe two arrows of BPMN. A solid arrow with a filled head is a sequence flow, the order of steps within one process; a dashed arrow that starts at a small open circle and ends in an open head is a message flow, a message passing between two participants.
More welding symbols
The same shape elsewhere
Browse symbols drawn with arrows, circles or lines.
Sources
- Welding Theory and Application, TM 9-237, 1967, Department of the Army (Internet Archive), Chapter 11, section II; glossary
- Scheme of symbols for welding, IS 813:1986, Bureau of Indian Standards (Internet Archive, Public.Resource.Org), Table 1
Researched, edited and approved by Rory Hansen before publishing. Last reviewed September 25, 2026. How we research
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