2.2.1. Signs to diagrams 504.1 (S2‑2‑1, see Figure 2-2), 505.1 (S2‑2‑2, see Figure 2-3), 506.1 (S2‑2‑3, see Figure 2-4) and 507.1 (S2‑2‑4, see Figure 2-5) indicate the presence of a junction. The priority route is indicated by the thicker part of the route symbol. This may not necessarily be a route of the same status or with the same route number. The signs may be used only on the priority route, i.e. the width of the part of the symbol indicating the approach arm must not be varied. Diagram 505.1 must not be used on an approach that does not have priority at the junction. Where advance warning of the junction is considered necessary on the non‑priority approach, diagram 501 with the appropriate distance plate should be used.