The Brake Gauge are design to tell the engineer of how much pressure the brake cylinders on the locomotives.
When the Engineer moves the Brake Lever the hands in the Gauges goes to the pressure.
Each of the gauges have red and black hands to tell the engineer how much pressure are in the brakes.
In the Steam locomotives each brake gauge looks like are round with numbers and a pointer like that of the hands on a clock face they are always seen in the cab.
In some electric and diesel locomotives the almost look like that same thing and they sometimes look like wristwatches.