OO9 is 4mm to the foot scale (that is OO or 1/76) but using 9mm track gauge (the same size as N gauge). This is...
A static mainline is a dummy mainline track on a viaduct or embankment that spans the width of a smallish baseboard. It is used as a scene-break to hide the other side of the baseboard, but, as it doesn't go anywhere, it's generally not...