Backing

From GAWDAwiki

Backing is a material or device placed against the back side of the joint, or at both sides of a weld in electroslag and electrogas welding, to support and retain molten metal. The material may be partially fused or remain unfused during welding and may be metal or non-metal. ^[1]

References

1. http://www.bocindustrial.co.uk/bocindustrial/technical/glossary/a.asp