Apple MacBook Pro A1502 logic board boardview for board 820-4924-A, delivered as a 576 KB .brd file. A1502 is the 13-inch Retina model, and the 820-xxxx code with its revision letter is Apple's logic-board part number, which you should read off the board itself before comparing. BRD files open in OpenBoardView, FlexBV or similar viewers, letting you locate components, follow signals and power rails such as PPBUS and the standby supplies, and find good measurement points when diagnosing a short.
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 @boardviews. 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.