Gauge measure (Narrow Gauge)

Trains run within the gauge of the railway structure. This consists of two iron rails, placed in parallel and fixed on sleepers, which rest on the stone ballast layer. The gauge, or track width, is the distance between the two rails. This can be wide or narrow, with different distances between each type.
Not all railways are the same, and may vary in components or gauge between different countries, regions or locations. In Portugal and Spain, a large part of the network is built in Iberian gauge (1668 mm width between the rails).
In the other European countries, on the other hand, the European gauge (1435 mm between rails) is more common. However, examples of narrow gauge railways can be found everywhere. This is the case of mines, with lines in mining or industrial gauge (600 mm) or metre gauge lines (1000 mm), often built-in areas with irregular terrain, as is the case in Portugal with the lines north of the Douro valley.
Popularly known on the railway as a gauger guise, the gauge rule allows the track width to be kept within regulatory tolerance limits. It is used to measure and correct the distance between the rails - the track gauge - and the rail inclination. There are wide track gauges to measure the 1668mm gauge and narrow track gauges for the 1000mm gauge.