Small 136 KB RAR archive named for an N55SF main board, revision 2.0, most likely an ASUS N55SF board file, though the name does not state its contents. At this size it could hold a boardview or similar data rather than a full BIOS image, so inspect it after extraction. Boardview files open in tools like OpenBoardView or FlexBV to locate components, nets and test points. Confirm the PCB revision printed on the board matches 2.0 before relying on any layout data.
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 @schematicslaptop. 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.
7-ZipWinRARThe Unarchiver (macOS)