A backyard railroad is a privately owned, outdoor railroad, most often in miniature, but large enough for one or several persons to ride on. The rail gauge can be anything from 2+1⁄2 in (64 mm) to 7+1⁄2 in (190.5 mm) or more. Smaller backyard or outdoor railroads that cannot be ridden are called garden railroads. Some backyard railroads use full-size rolling stock, such as the former 3 ft (914 mm) narrow gaugeGrizzly Flats Railroad owned by railfan and Disney animator Ward Kimball.
Tracks for the layout can be either portable (i.e. removable), or permanent. The former may be of fairly simple weldedsteel construction, but the latter are usually built from miniature steel or aluminium rails attached to wooden, plastic or even concrete sleepers (US: ties), and put on a proper foundation of crushed stone ("track ballast"), just as in full size. Turnouts (US: switches) are also fabricated from these basic materials. Usually, prototypical appearance is sought for, but some portable tracks may not closely resemble real railroad tracks. In many cases dual-gauge track (i.e. 3+1⁄2 in (89 mm) and 5 in (127 mm) gauge) may be used to allow locomotives and rolling stock of different gauges to run.
Rolling stock is often modeled after real railroad equipment, as far as being painted with logos of past or existing railroads. Boxcars, flat cars, tank cars and cabooses are common. For passenger use, special cars are constructed, with a low center of gravity for safety.