Direct Answer
Weld symbols follow AWS A2.4 and consist of a reference line, arrow, and tail. The symbol below the reference line indicates the arrow side (near side) of the weld; the symbol above indicates the far side. The weld size appears to the left of the symbol, weld length to the right, and the tail carries the weld process or specification reference.
Full Explanation
Common structural welds: fillet weld (triangle symbol), CJP groove weld (open rectangle or specific groove preparation symbol with 'CJP' note), PJP groove weld (similar but with depth of prep). A filled circle at the reference line intersection means 'weld all around.' A flag at the reference line bend means 'field weld.' The number to the left of a fillet weld symbol is the leg size in inches (e.g., 3/8 means a 3/8" fillet). If the effective throat is specified instead, it will be called out differently.
What This Means for Your Shop
Your welders must be able to read weld symbols and understand the difference between shop and field weld callouts. Field welds on shop drawings are the erector's responsibility — they must not be pre-applied in the shop.
Common Mistakes
Confusing the arrow side and far side weld symbols, resulting in a weld on the wrong face of the joint. Also: applying a field weld in the shop because the symbol was misread.
Recommended Process
Post an AWS A2.4 weld symbol reference chart in the shop. Require your welders to complete AWS structural weld symbol training. For complex weld conditions, have the detailer add a note clarifying the intent.