In welding symbols, what does a square symbol specify?

• A. A consumable insert
• B. A backing bar
• C. A spacer
• D. A weld size indicator

Answer: (A)

In welding symbols, a square mark used on the symbol denotes the presence of a consumable insert in the joint. This means an insert material is placed into the weld area before welding and is consumed during the process, contributing to the weld with added material or specific shaping. This is different from a backing bar (which is shown by separate backing-related cues on the symbol), a spacer (which is not indicated by a square and is typically conveyed by dimensions or separate notes), or a weld size indicator (which is just a numerical callout for the weld throat or leg length). When you see the square symbol, you should refer to the drawing notes to identify the insert material, its size, and whether it remains or is entirely consumed in the weld.