Asus PSCH-SR/SCSI - Manual (Page 20)

2-2 Chapter 2: Hardware information
2.2 Motherboard installation
Before you install the motherboard, study the configuration of your chassis
to ensure that the motherboard fits into it.
Do not overtighten the screws! Doing so may damage the
motherboard.
2.2.1 Placement direction
When installing the motherboard, make sure that you place it to the
chassis in the correct orientation. The edge with external ports goes to the
rear part of the chassis as indicated in the image below.
2.2.2 Screw holes
Secure the motherboard to the chassis with nine (9) screws on the holes
indicated by the circles.
Make sure to unplug the power cord before installing or removing the
motherboard. Failure to do so may cause you physical injury and
damage motherboard components.
Place this side towards
the rear of the chassis