Conforming modules Modules that are freely interchangeable in every way with all other conforming modules built to these standards. Married sets Any group of modules in which the individual modules cannot be used separately for some reason. Married sets typically consist of modules that do not conform to our interface standards between themselves, but conform to the interface standards at both ends of the set. Any modules which are built for use in a layout comprised of modules conforming to these standards which cannot be indiscriminately turned around and connected on their own to the rest of the layout. Non-standard conforming modules are usually built in married sets of several modules for some particular purpose or effect and conform completely with these standards at their opposite interfacing ends.
Typical lengths are four, six or eight feet.
Modules may be built to other lengths, so long as other modules are provided which bring their combined lengths to an even multiple of feet. Deeper modules are permitted since the truly crucial dimension is the centerline spacing of the standard double track mainline. Module legs should be adjustable to allow for levelling the layout. MLS module legs provide this feature. While double-tracked modules are the norm, modules may have as many tracks crossing them as you want to lay.