The "runway threshold bar" marking indicates:

The runway threshold bar marking serves a critical role in signaling pilots about the available landing area of a runway. Specifically, this marking indicates the beginning of the runway that is available for landing. This is particularly relevant when a runway has a threshold displacement due to obstacles or other terrain features that necessitate the designated landing zone to start further down the runway than its physical beginning. By understanding this, pilots can better judge where to initiate their landing approach, ensuring that they touch down within the appropriate section of the runway that is clear and safe for landing, thus contributing to overall operational safety.