Epson Progression U12 - Manual (Page 67)

4. Lower the back end of the subassembly into the computer.
If necessary, fit the post beneath the back right edge of the
subassembly into the hole on the top of the power supply.
Then lower the subassembly all the way down.
5. Gather the power supply and drive cables in the clasps on
the side of the subassembly; then shut the clasps.
2-10 Accessing Internal Components