Preparing The Case
Most cases support a range of motherboard sizes, each with a few different mounting points. These points are meant to connect a layer of the motherboard called the "ground plane" to the case's mounting tray, reducing signal crosstalk due to radio frequency interference (RFI). Thus, the mounting points are grounded.
Solder points around mounting holes ground this motherboard to the chassis through brass standoffs, which are included with the case.
Misaligned mounting points could contact a "hot" trace on the motherboard's back side, so case manufacturers usually make them removable via brass spacers called "standoffs". It's important to observe the motherboard's mounting hole positions and place a standoff in each corresponding tray location. A mistake made here could potentially damage the board, but the most likely result is just a system that simply refuses to "power on".
Standoff locations must exactly match the mounting holes of the motherboard.
Most motherboards use a custom port arrangement and include a customized rectangular cover plate that snaps into a standardized rectangular hole on the case. Cases typically include an old-fashion standard plate that must be snapped out before inserting the new, custom one.
Note that the upper tabs hang down because the cover plate usually arrives in a semi-flattened state. These need to be bent approximately ninety-degrees from the surface to prevent them from blocking nearby ports during motherboard installation. The left tab in the photo below has been bent to the proper orientation.