In structural steel fabrication, a fillet weld may legitimately be described by which of the following terms based on its profile or application?

Introduction / Context:
Fillet welds join two members at roughly right angles forming a triangular weld profile in the joint (e.g., lap, T, or corner joints). Depending on detailing and execution, the face of a fillet weld may be concave, flat, or convex, and corner applications are often referred to as mitred connections in shop terminology.

Given Data / Assumptions:

• We address terminology used in practical steelwork.
• Options reference the weld face profile and a corner (mitre) application.

Concept / Approach:
A fillet weld is not limited to a single surface contour. Weld face profiles are intentionally specified for stress distribution and aesthetics: concave faces reduce stress concentration at toes; convex faces can add throat but may create higher toe stresses. In corner joints cut at angles (mitred), the connecting welds are commonly still fillet welds along the meeting edges, hence the colloquial “mitre weld.”

Step-by-Step Solution:
Recognize that concave and convex define fillet face geometry. Acknowledge that corner/mitred joints frequently use fillet welds along the edges. Therefore, a fillet weld may be termed concave, convex, or mitre in context—making “All the above” correct.

Verification / Alternative check:
Fabrication standards allow specifying fillet size and contour (convex/concave) and detailing typical corner (mitre) joints with fillets; shop drawings and WPSs reflect this practice.

Why Other Options Are Wrong:
Selecting any single profile ignores the accepted variety of fillet faces and applications; the comprehensive choice is correct.

Common Pitfalls:

• Assuming “mitre” implies a butt weld; many mitred corners are still fillet-welded.
• Believing only flat/concave faces are allowed; convex faces are also used when specified.

Final Answer:
All the above.