1. Water gauge and blowdown valve - paramount to the safe running of the locomotive, the boiler water level must be kept visible in the glass. If the water level is too high, the locomotive will prime, as water rather than steam is passed to the cylinders, and most of that will be passed up the chimney! In full size this, is very dangerous and can result in severe damage to a locomotive's cylinders.
Too little water and there is a risk of uncovering the top of the firebox. This can result in the production of 'flash steam', quickly increasing the pressure, and if unchecked could damage the boiler or cause an explosion. For these reasons, if in any doubt, the locomotive should be stopped and the water level investigated and corrected. When bubbles or grime appears in the glass, the blowdown valve allows the water in the glass to be blown out to the ground, cleaning the glass tube.

2. Firehole door - the place where coal is added to the fire. Although Keith's is hinged at the side, they can be hinged at the bottom, or may be sliding doors as fitted to Fred's. The door is normally kept shut to stop cold air going in and cooling the boiler. Coal should be added evenly across the fire, as if there are air holes in the fire, steam will not be generated properly.

3. Boiler pressure gauge - indicates the current steam pressure in the boiler. Most miniature steam boilers run at between 80 - 100 p.s.i. If the pressure falls much below 60 p.s.i. there is probably not enough power left to pull a train, and the fire will need to be stoked up. Any pressure in excess of the maximum permitted should automatically released by the saftey valve(s). Some locomotives have an additional 'steam chest' pressure gauge to monitor the pressure of steam arriving at the cylinders.

4. Steam turret - normally the highest point on the boiler (except where there is a steam dome), and is a take-off point for fairly dry steam used to supply small items like the pressure gauge, blower, and injectors.

5. Blower valve - controls a small jet of steam directed up the chimney. This is used to maintain the airflow (draught) through the fire when the locomotive is stationary, as there is no natural draft in a horizontal boiler. On the move the exhaust steam from the cylinders (the chuff, chuff,) draws the fire.

6. Injector steam valve - this controls steam feed to the injector; a cunning device that uses steam to feed cold water into the boiler.
Some locomotives also have axle driven water pumps, and all are fitted with an emergency hand pump.

7. Reversing pole - used to control the relative position of the valves that feed steam to the cylinders. Pushed fully forward allows the maximum steam feed for forward movement, normally used for starting. As speed increases, the lever may be ratcheted towards the mid-position, increasing the 'cut-off'; saving steam by closing the cylinder's valves earlier in each cycle, and allowing the steam more time to expand in the cylinders. In mid gear, the valves pretty much close any major steam supply to the cylinders, so this is the position to park a locomotive in safety, without the chance of a runaway. The lever is similarly pulled backwards for reverse motion. On some locomotives this is done by a wheel driving a gear to create the same effect.

8. Handbrake - purely a 'parking brake' for the locomotive, not used for stopping a train. On a tank engine, this would brake the driving wheels. Where the locomotive is fitted with a tender, it is normally sited there and clamps the tender wheels.

9. Whistle valve- the one thing everyone wants to play with - to blow the steam whistle ! Normally the whistle is hidden away underneath the running boards of the locomotive, as getting a decent whistle note requires a well over-scale sized whistle.

10. Regulator valve - the main valve that allows boiler steam to be fed to the cylinders, to power the locomotive. Where sufficient boiler pressure is available, the more it is opened, the faster the locomotive goes. However, care is required when starting a train, particularly with a heavy load, to prevent 'wheel slip'. This is when the driving wheels loose adhesion with the rails, a condition that can cause extensive damage if unchecked.

11. Cylinder drain cock lever - this lever, which may be connected by a solid rod or cable, operates a set of valves, one located at the bottom of each motion cylinder. The drain cocks are 'opened' before opening the regulator on a stationary locomotive to allow any cool condensed water to be expelled. Since water cannot be compressed, it can lock up the cylinders or cause severe damage if not removed. Normally the drain cocks are opened for 30 - 40 seconds as the locomotive is first moved under steam for the day, and as required after stationary periods.

12. By-pass valve - this is fitted where a locomotive has an axle pump, which pumps continuously as the driving wheels rotate. The valve allows the driver to choose how much of the pumped water goes into the boiler, or by-passes it, being redirected back to the water tank or tender. This is to prevent the boiler from being overfilled with water on a long run.

13. Vacuum brake gauge - on a steam locomotive, vacuum for use in applying the brakes on the locomotive or the train, is usually created using a steam ejector. The gauge allows one to see how much braking power is available. Vacuum gauges normally read 0 - 15 in. hg (inches of Mercury).

14. Vacuum brake valve - used to apply the vacuum brakes on the locomotive (or train when fitted).