Archive for the A300H, 6.48 MB, with an SM suffix that usually means service manual; the code matches the Samsung Galaxy A3 SM-A300H pattern, though no brand is stated. Service manuals of this type typically combine disassembly guidance, parts references and board-level diagrams useful for tracing faults. Extract the RAR and open the contents with a PDF reader. Before relying on component positions or values, verify the A300H model code on your unit, since sibling variants may use different boards.
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.