Boardview for the Apple X3087 main logic board, part number 820-03597, with the 051-10340 schematic reference included in the name. The .brd layout shows component placement, part designators, nets and test points on both sides of the board, which helps when hunting a short or measuring a rail found in the schematic. It opens in viewers such as OpenBoardView, FlexBV or similar tools. Match the 820 number silkscreened on the logic board before trusting pin locations.
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 @Satale_bios_esquemas_Laptop. 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.