IBM System x3550 M4 - Page 350

3. Fasten the two thumbscrews (one is near PCI slot 2 and one is between fans 4
and 5).
4. Rotate the fan assembly bracket down toward the rear of the server.
Figure 241. System-board standoffs
Figure 242. Thumbscrews engagement
332 IBM System x3550 M4 Type 7914: Installation and Service Guide