Epson AcuLaser MX20DNF - Manual (Page 188)

4. Align the corners of the printer and the unit, then lower the printer gently onto the unit so that the
connector and two pins on the top of the unit fit into the terminal and the holes on the bottom of
the printer respectively.
Note:
You can install up to two optional paper cassette units. When you install two units, stack them up
against each other, and then place the printer on them.
5. Pull the paper cassette out from the unit.
Epson AcuLaser MX21/MX20 Series User's Guide
Installing Options 188