The rail is the essential element of any railway. Although overshadowed by the rolling stock that runs on it, the metal rail, which evolved largely in Britain, appears in myriad variations. The type most often used today, with its mushroom-shaped profile, is known as the Vignoles rail. It is made by rolling an extruded piece of high-grade steel up to 20 times. Bridge rails and double-headed rails, made of iron and welded together, were widely used in the 19th century. Double-headed rails were laid on the Lötschberg line when it was built at the start of the 20th century. The bridge rail was not a success, being almost completely inflexible and therefore unsuited to laying curves. The first rails used in Switzerland were imported from Britain for the Zurich-Baden line, popularly dubbed the «Spanish bun railway», which opened in 1847. They were four metres long. Today, sections of rail can be over two hundred metres in length.

« A guide rail that would be useful on entrance would create a hindrance on exit, whereas a guide rail that creates little hindrance on exit would most probably be useless on entrance. »

Swiss Railways Federation Technical Commission, Report on 67th section meeting, 24.04.1889