Plain English Meaning
Black signs with a single white number beside the runway. The number tells you how many thousands of feet of runway are still in front of you.
Full Definition
Airport signs located along the side of a runway that show the distance, in thousands of feet, of runway remaining ahead of the aircraft. Each sign displays a single white numeral on a black background, with the number indicating thousands of feet remaining (for example, a sign showing '3' means 3,000 feet of runway remain).
Context Anchor
Seen beside some runways during takeoff, landing roll, or taxi on the runway.
Why Pilots Care
They give real-time distance awareness so pilots can decide whether to continue or abort before running out of pavement.
Analogy
They work like mile markers in reverse: instead of showing how you have gone, they show how much distance is still .