RAR archive for the QT6A motherboard, with an MB-C suffix that likely marks revision C, 152 KB in size. The name does not identify the content type, and the small size points toward boardview or layout data rather than a complete schematic. Extract and open it with a suitable viewer to check. Boardview files help find components, nets and test points when diagnosing shorts or missing rails. Confirm that the board code and revision printed on the PCB match before working.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.