HP Officejet Pro X551 Printer series - Manual (Page 169)

4. Lower the platen by pressing down on the
green tab. This will cause the product to try to
feed the sheet through the print zone. You may
need to gently pull on the sheet if it does not
feed. Remove the sheet.
5. Lift the green tab to place the platen back into
its operating position.
ENWW Clear jams 155