HP Designjet T1120 SD-MFP Guide De Référence Rapide page 35

down the Paper Backward or the Paper Forward key. If the document will not
respond to these keys, remove it manually in the following way.
1. Flip the touch screen backwards.
2. Simultaneously slide the lid release buttons towards the scanner's center until
you feel them unlock.
ENWW
There is a paper jam
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