Body Panel Replacement, Alignment, and Structural Repair
Panel replacement
Understand bolt-on versus welded panels. Bolt-on panels (fenders, doors, hoods) use fasteners and alignment shims; welded panels (quarter panels, rockers) require cutting, plug welding, and seam sealing. Before removal, record gap and flush measurements. Know that structural components (frame rails, pillars, aprons) require sectioning per manufacturer procedures.
Alignment
Panel gaps should be even and consistent; use gap gauges or feeler gauges. Adjust hinges, latches, and shims to correct misalignment. Diagonal (X) measurements confirm structural squareness. When replacing a welded panel, tack-weld and check fit before final welding to avoid distortion.
Structural repair
Understand that structural repair restores crash energy management; never straighten a crumple zone in a way that compromises design. Use correct weld types: MIG plug welds replace factory spot welds; stitch welding adds strength. Heat input control minimizes distortion. Know that high-strength steel (HSS) may require specific welding procedures and should not be heat-treated indiscriminately.
Traps and rule of thumb
Trap: assuming any weld is acceptable - weld type, spacing, and material must match OEM specs. Trap: over-shimming a door instead of correcting hinge or pillar alignment. Rule of thumb: fit before finish - always dry-fit and check gaps before final welding or painting.