Boardview for the Apple logic board 820-2838, in BRD form inside a 72 KB RAR archive. No revision letter is given, so check the full 820 number printed on the PCB. BRD files open in OpenBoardView, FlexBV and similar viewers, which show part placement, pin nets and both board sides. That makes it fast to find test points, locate decoupling capacitors on a shorted rail, check connector pinouts and match schematic parts to their physical position during 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 @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.
7-ZipWinRARThe Unarchiver (macOS)