Apple logic board boardview for board number 820-3787, revision A, in BRD format at 868 KB. The name gives no model, so identify the machine by matching the 820-3787 number printed on the logic board itself. Apple uses the 820-xxxx series for main logic boards across MacBook and iMac lines. Open it in OpenBoardView, FlexBV or a similar viewer to look up components, follow nets between chips, locate test points and track down shorted rails during board-level 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 @boardview. Enginerys does not host this file.
How to open a .brd file
The most common boardview extension. Several unrelated formats share it, which is why one viewer opens a .brd and another refuses it.