Signal transition, reference connection and remaining stubSignal transition, reference connection and remaining stubL1 signalL2 referenceL3 signalL4 referencestubREVIEW BOTH PATHSSignal via: L1 → L3Reference via: L2 ↔ L4Clearance at other layersUnused signal-via barrelDefined drill depth / diameterThe field and return pathstill require circuit review.A layer transition needs a reference transition, not just a new trace layer.Schematic cross-section; no exact antipad, spacing, impedance or fabrication approval is implied.