A15 · Reference edition 2026.11
The 3-2-1 layout concept — Review and interpretation
Three, two and one contact groups describe a conceptual constraint arrangement for a suitable rigid part. Contact geometry still needs review.
Scope and purpose
Review the record before drawing a conclusion. Look for missing context, ambiguous labels and claims that exceed the evidence. The purpose is to identify what can be understood from the record and what still requires a separate assessment.
Working notes
This reference collection concerns light, offline dimensional-inspection layouts. It brings locating concepts, component descriptions and revision records together without substituting for an engineered fixture design. The drawings are original explanatory diagrams. Reference IDs identify documents, not commercially tested products. Read the scope and limitations alongside each example, and keep the actual part drawing and inspection requirements available when reviewing a proposed layout.
Practical example
Sketch three primary supports before adding secondary and tertiary locators.
| Reference record | Interpretation |
|---|---|
| A15 | The 3-2-1 layout concept |
| Scope and purpose | Three, two and one contact groups describe a conceptual constraint arrangement for a suitable rigid part. Contact geometry still needs review. |
| Limits and interpretation | Thin walls and flexible parts need analysis beyond the rigid-body sketch. |
Review checklist
Read the record without relying on memory; check every label; identify uncertainty; decide whether a specialist review is required; retain the original observation.