HP LaserJet 4345 Multifunction Printer series - Manual (Page 25)

Locking and unlocking optional accessories
For more stability to prevent the MFP from tipping over, the optional 500-sheet feeders and
the cabinet are automatically locked to the bottom of the MFP. When accessories are
installed, verify that the lock on each accessory is in the rear (locked) position.
To unlock the accessories, slide the lever to the forward (unlocked) position.
ENWW MFP parts and accessories 11