Stud contact is a system of electrification for model railways. It was popular in the days before the widespread use of plastics since it permits the use of metal sleepers or track bases, and does not require an insulated section to be inserted in each wheel set.

The system is a modification of the third rail electrification

Third rail

A third rail is a method of providing electric power to a railway train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost...

 system designed for use on systems where an actual third rail would be unprototypical. Studs are laid at regular intervals, generally down the centre of the track. They are connected electrically and insulated from the running track. A flat ski collector under the loco that is always contact with at least one stud acts as the collector. Because the collector acts on a small area, the stud, the action of the collector is to clean the stud. This ensures the system has good electrical contact. This means the system works well even on track covered in oil, sand and the general detritus of a garden railway

Garden railway

A garden railroad or garden railway is a model railway system set up outdoors in a garden. While G is the most popular scale for garden railroads, 16 mm scale has a dedicated and growing following especially in the UK. Model locomotives in this scale are often live steam scale models of British...

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While the system was generally confined to the larger gauges (O and above) the Märklin

Märklin

Gebr. Märklin & Cie. GmbH or Märklin is a German toy company. The company was founded in 1859 and is based at Göppingen in Baden-Wurttemberg. Although it originally specialised in doll house accessories, today it is best known for model railways and technical toys...

 company has for many years used a version of the system (known as the Märklin system) for their HO gauge range.

Peco Products

Peco

Peco is a UK-based manufacturer of model railway accessories, especially trackwork, based at Pecorama, Beer in South Devon.Peco is the collective name for the Pritchard Patent Product Company Ltd, Peco Publications and Publicity Ltd, and Pecorama...

 make studding for their 00/H0 track range. Part nos SL-17 for track and SL-18 for turnouts

Railroad switch

A railroad switch, turnout or [set of] points is a mechanical installation enabling railway trains to be guided from one track to another at a railway junction....

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Modern use of the system is largely restricted to garden railways where it has the advantage of being compatible with unmodified live steam

Live steam

Live steam is steam under pressure, obtained by heating water in a boiler. The steam is used to operate stationary or moving equipment.A live steam machine or device is one powered by steam, but the term is usually reserved for those that are replicas, scale models, toys, or otherwise used for...

 locomotives. While it is possible to insulate model live steam locomotives so that they can operate on two rail electrified

Third rail (model railroading)

The use of a third rail in model railroading is a technique that is sometimes applied in order to facilitate easier wiring.-Two-rail versus three-rail system:Early toy trains used two metal rail tracks like most real trains...

track, it is difficult and trouble prone especially where the model is likely to come into contact with water.

Reference

• Stud Contact Electrification by Ernest F Carter. Percival Marshall published 1949