Direct Answer
A field weld flag (a pennant or flag symbol at the bend of the weld reference line) indicates that a weld is to be made in the field after erection — not in the shop. Field welds are typically more expensive, require field welding procedures and qualified field welders, and need field inspection. Do not apply field welds in the shop — they are deliberately left for field completion.
Full Explanation
Field welds are used where shop welding would prevent erection (e.g., a moment connection flange weld that must be made after the beam is in place) or where the connection requires field fit-up adjustments before welding. Field welds require the same AWS D1.1 compliance as shop welds but are performed under field conditions — weather protection, access constraints, position limitations — making quality control more challenging. The erection subcontractor is typically responsible for field welds, though some fabricators provide field welding services.
What This Means for Your Shop
Clarify contract responsibility for field welds at project kickoff. Is field welding in your scope? In the erection subcontractor's scope? In a separate specialty subcontract? The answer affects your bid, your manpower planning, and your inspection obligations.
Common Mistakes
Shop-welding a connection that was designated as a field weld because 'it would be faster.' The engineer designated it as a field weld for a reason (sequence, fit-up, access) — performing it in the shop may make erection impossible.
Recommended Process
Identify all field welds on the shop drawings during your drawing review. Confirm with the GC who is responsible for each field weld. If you are responsible, include field welding in your QC plan and ensure field welders have appropriate D1.1 qualifications.