It's pretty simple, it's a case for the Beaglebone Black with pegs that fit through the screw holes and mate to hollow posts on the top case to hold together. They should be tight enough to friction fit in place.The included Asterisk branding on top is just a bonus, although it would be a bit of a drawback for a BBB that's not being used as an Asterisk based PBX.Update: Now there's a plain top version AND the openscad source file for you to modify if you'd like. Non-PBX beaglebone problem solved!