Lexmark T420 User Reference page 142

3
Press the side door firmly into place, making sure that the two tabs are in place, and that the
ridge on top of the side door aligns with the ridge on the printer.
4
Close the upper front door and multipurpose feeder door.
5
Reconnect all cables on the back of the printer.
6
Plug in the printer power cord, and turn the printer on.
Ridge
142
Tabs