Plug or slot weld
A small rectangle on the reference line: a plug or slot weld, made through a hole or slot in one member of a lap joint.
How to read it
Plug and slot welds are made through holes or slots in one member of a lap joint, joining that member to the surface of the other member where it shows through the hole. A slot weld is made in an elongated hole. The hole may or may not be completely filled with weld metal.
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 symbol as a plug weld and notes the United States name, plug or slot weld.
Read next
- Next in Welding symbolsSpot weldA circle on the reference line: a spot weld, a resistance weld that joins sheets at a single point.
- The same shape in Blueprint symbolsStairsA staircase, seen from above. The arrow shows the direction of travel from this floor, labelled with the direction and the number of risers.
More welding symbols
The same shape elsewhere
Browse symbols drawn with arrows, lines or squares and rectangles.
Sources
- Steelworker, Volume 1, NAVEDTRA 14250, 1996, Naval Education and Training Professional Development and Technology Center, U.S. Navy (Internet Archive), Chapter 3, Drawings and specifications
- Welding Theory and Application, TM 9-237, 1967, Department of the Army (Internet Archive), 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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