Epson Progression U12 - Manual (Page 120)

Follow these steps to install a new hard disk drive (or reinstall a
drive you removed) in the internal bay:
1. Your hard disk drive may have come with mounting frames
attached to each side of the drive, as shown below. On one
side, there may also be a plastic guiderail. (If your drive
came without frames or a plastic guiderail, skip to step 3.)
mounting frames
Installing and Removing Drives 4-17