Epson B 310N - Manual (Page 112)

Installing Options 112
Note:
Keep the upper rear printer cover, since it must be in place should you remove the duplexing
unit later.
3. Insert the bottom side of the duplex unit first, and then attach the duplex unit.
Uninstalling the Optional Duplex Unit
Follow the steps below to uninstall the duplex unit.
1. Turn off the printer.