Watchguard Firebox SSL Core Hardware Manual page 17

The hard drive is not a hot swap device. Failure to turn the
Firebox off before installing the hard drive can result in
damage to the hard drive.
2 On the front right side of the Firebox, look for the door
covering the hard drive slot.
3
Lift the door and find the two release tabs for the hard drive
tray.
Firebox® SSL Core Hardware Guide
Installing the Hard Drive
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