Welding Symbols, Joint Design, and Vehicle Body Construction
Reading the symbol
Welding symbols follow AWS A2.4 conventions. The reference line carries the weld symbol; the arrow points to the joint; the tail may carry the process or specification. A symbol above the reference line is on the arrow side; below is the other side. Fillet size is shown to the left of the fillet symbol, length to the right, and pitch after a dash. A circle at the kink means weld all around; a flag means field weld. A spot weld is shown as a circle with size and spacing.
Joint design and body construction
Collision repairs use lap, butt, tee, corner, and edge joints. Fit-up controls penetration: excessive gap causes burn-through; tight fit can cause incomplete fusion. Plug welds are common on flanges where a factory spot weld cannot be reached. Unibody vehicles use crumple zones and high-strength steel in occupant-cell areas; body-on-frame vehicles use separate frames. OEM service information, not a generic symbol chart, defines weld location and count.
Worked example
A symbol shows a fillet weld, 5 mm leg, 30 mm length, with a 60 mm pitch. The reasoning: each weld is 30 mm long, and the 60 mm pitch is center-to-center spacing, so the gap is 30 mm. If the arrow points to a lap flange, the fillet goes on the arrow side unless the symbol is below the line.
Traps
Reading the arrow side backwards; treating a field-weld flag as a weld-all-around; assuming an aftermarket panel uses the same weld schedule; using a continuous weld where the OEM specifies stitch welds.