Co-authored by Stefan Frey <stefan.frey@...>.
Thanks to Stefan for the half-hex pictures.
For 1825, to help recognising allowed track laying on some board edges.
Applied to Unit 1 only, at the borders with Unit 2 and kits R1-3.
All Unit 1 'open' attributes have been removed.
Q11 (Crewe) SW is now impassable.