Apple iPhone 7 Plus archive, a 14.0 MB RAR whose name does not state the contents, so extract it and identify each file before use. The larger size suggests it may combine several documents such as schematics, boardview data or layout images. These are used to locate parts on the logic board, follow power and signal lines, and find test points when diagnosing shorts, missing rails or audio and baseband faults. Boardview formats need a matching viewer, and PDFs open anywhere. Verify that board identifiers match the device under repair.
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 @schematic_mobiles. 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.