Fujitsu M10-4 Service Manual page 271

Figure 10-4 Removing an internal disk
3.
Carefully remove the internal disk from its slot.
Note - Place the removed internal disk on the grounded antistatic ESD mat.
4.
When reducing an internal disk, install the the internal disk filler unit in the
slot from which the disk was removed.
Chapter 10 Maintaining the Internal Disks 257