HP Color LaserJet Enterprise M855 Printer series - Manual (Page 127)

5. Grasp the edges of each staple cartridge and
firmly pull up to remove the staple cartridges
from the staple cartridge unit.
6. Press down on the jam-release at the back of the
saddle-staple cartridge, push up on the plate at
the front of the cartridge, and then remove any
jammed staples.
1
2
3
7. Press down on the front of the saddle-staple
cartridge close it.
ENWW Clear jams 119