- Trains I enjoy model railroading - HO scale thank you. I build modules that vary in width anywhere from 1 foot to 3 feet, with lengths ranging from 3 feet to 8 feet. Each module has a separate setting (even different decades). I have completed a switching yard, a small industrial park, and a farm scene. The common thread is that all modules are connected by a mainline that runs through them all.www.mrollins.com/rail.html