Schematic in PDF format for the Apple logic board 820-3023, compressed in a 1.42 MB RAR archive. Apple identifies its main boards with 820-series numbers silkscreened on the PCB, so this document applies only to boards carrying that exact code. Technicians use these drawings to follow power rails, locate the source of a short, read the expected voltages on each line and understand the startup sequence around the SMC. Check the board number carefully, since neighbouring 820 numbers often belong to different machines or revisions.
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.