Asus DSBF-DM/SAS - Manual (Page 26)

2-6 Chapter 2: Hardware information
6. Before installing the motherboard
into the chassis, locate the standoffs
that should match the eight (8) CEK
spring screw holes.
8. Secure the motherboard with nine (9) screws. Refer to section 2.2.2 Screw
holes for illustration.
Make sure that the standoffs perfectly match the CEK spring screw holes;
otherwise, you can not install the CPU heatsinks properly.
Standoffs for CPU1
Standoffs for CPU2
7. Install the motherboard with the
external I/O ports toward the
chassis rear panel. The CPU
sockets should be right on top of
their respective standoffs.
Socket for CPU2 Socket for CPU1