In aviation, a yellow demarcation bar is a 3-foot (1 meter) wide yellow line that signifies the boundary between a non-runway surface and a displaced threshold. Specifically, it delineates the end of a blast pad, stopway, or taxiway and the beginning of the portion of the runway that can be used for takeoffs (but not landings). Because the surface preceding the bar is not built to withstand the impact of a landing aircraft, the bar serves as a critical visual warning to pilots that they must not touchdown before crossing it. The bar is painted yellow because it is technically located on a "non-runway" surface (like a taxiway or blast pad), whereas markings on the actual runway are always white. Seeing this bar from the air tells a pilot that the area behind it is purely for "overrun" or "blast" protection and is not part of the active landing strip, ensuring the structural safety of the aircraft and the pavement.