Layout edge

The layout edge is the outer rim of the baseboard — the boundary between model and floor. It matters for planning because a train that derails here has a long way to fall: experienced planners keep main tracks at least about 10 cm from the front edge, or protect them with a raised fascia. Track that overhangs the edge simply cannot be built — unless the edge is deliberately intended as a transition to an adjoining module or as the starting point for a later expansion.