Seagate NAS Pro 4-Bay Manual page 56

Full tray: Unfasten the four pins and remove the hard drive from the tray. To insert the new hard drive,
.gently bend the left side of the tray and connect it to the two pins on the right
.Release the left side of the tray and connect the remaining two pins to the hard drive .3
Insert the hard drive tray into the NAS Pro's bay. Push it into the bay as far as it will go before closing the .4
.tray handle
56 4/28/15 Seagate NAS Pro 2-Bay | 4-Bay | 6-Bay