Sun Microsystems Enterprise 250 Owner's Manual page 215

Push down on the top edge of the backplane and pull it away from the posts.
4. Slide the backplane out of the opening at the base of the disk cage.
Place the backplane on an antistatic mat.
Figure 9–2
What Next
To replace the UltraSCSI backplane, complete this task:
4 "How to Install the UltraSCSI Backplane" on page 182
Removing and Installing Backplanes and Cables
181