This article is a glossary of the main components found on a typical steam locomotive. The diagram, which is not to scale, is a composite of various designs in the late steam era. Some components shown are not the same, or are not present, on some locomotives – for example, on smaller or articulated types. Conversely, some locomotives have components not listed here. Details of the components TenderAttached rail vehicle that holds both water for the boiler and fuel such as wood, coal, or oil. Cab Footplate Compartment where the engineer (US+) / driver (UK+) and fireman control the locomotive and tend the steam supply and firebox. They achieve that using various devices, most of which are on the rear surface of the firebox, called the "backhead": a throttle lever or regulator, which controls the amount of steam entering the cylinders a reversing lever or (US term) Johnson bar, which controls the timing of the admission of steam into the locomotive's cylinders. This is required for two purposes. One is to reverse the locomotive's direction, e.g. when shunting. The other is to enable more fuel-efficient operation when the locomotive is running in a steady state: the throttle is set wide open and the power output is controlled by moving the reversing lever closer to its mid-point ("reducing the cut-off") to limit the amount of steam admitted to the cylinders. a train brake lever, which controls the application of brakes throughout the length of the train and a locomotive brake lever, controlling brakes on the locomotive only steam pressure gauges, which show the pressure of the steam in the boiler injector valves, which allow steam to force water into the boiler when needed water gauges, which allow the level of water in the boiler to be monitored mechanical stoker controls (when fitted to larger coal-fired locomotives) or oil feed controls for oil-fired locomotives lubricator glasses, which allow the flow of lubricating oil to be monitored a blower valve, which regulates the steam supplied to the blower (11) a whistle lever, which varies the steam supplied to the whistle (3) blowdown (or blow-off) cocks, which allow water to be ejected from the boiler to avoid concentration of impurities remaining after evaporation of steam. WhistleSteam powered whistle, located on top of the boiler and used for signalling (by the number and length of notes) and warning of approach. Reach rodRod linking the reversing