In the two-part marking system for indicating which rooms have been searched, what symbol represents a searched room?

In the two-part marking system used by fire fighters, an X is utilized to signify that a room has been searched. This method allows for quick and clear communication on the scene, especially in situations where visibility may be compromised. The X is prominently marked on the door or entryway of the searched room, making it easily identifiable for all members of the firefighting team. This practice is crucial for ensuring that no areas are overlooked during search and rescue operations, ultimately helping to enhance the safety of both victims and firefighters. The simplicity and visibility of the X make it an effective symbol for this purpose.