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.
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.
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.
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.
More welding symbols
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
Last reviewed September 25, 2026 by Rory Hansen. How we research