Samsung SCX-5639FR-XAA - Manual (Page 121)

Clearing paper jams
121 4. Troubleshooting
1 Pull the duplex unit out of the machine.
2 Remove the jammed paper from the duplex unit.
If the paper does not come out with the duplex unit, remove
the paper from the bottom of the machine.
If you still do not see the paper, go to the next step.