Symbol that is used when 100% penetration is required on one-side welds.

Symbol that is used when 100% penetration is required on one-side welds.

• A. Melt through
• B. Full penetration
• C. Penetration
• D. Root pass

Answer: (A)

Understanding how to indicate complete fusion on a weld that can be made from only one side hinges on the melt-through symbol. This symbol tells the welder to burn through the full thickness so the far side is welded as well, guaranteeing 100% penetration from the accessible side. It’s used specifically for one-side welds where you can’t rely on backing or access to both faces. Full penetration alone describes the result, but not the method or constraint of a single-sided weld; penetration by itself is too vague. Penetration or a root pass describe depth aspects or the initial root weld without conveying that the weld must melt through to the opposite face.

Understanding how to indicate complete fusion on a weld that can be made from only one side hinges on the melt-through symbol. This symbol tells the welder to burn through the full thickness so the far side is welded as well, guaranteeing 100% penetration from the accessible side. It’s used specifically for one-side welds where you can’t rely on backing or access to both faces.

Full penetration alone describes the result, but not the method or constraint of a single-sided weld; penetration by itself is too vague. Penetration or a root pass describe depth aspects or the initial root weld without conveying that the weld must melt through to the opposite face.