Seagate NAS Pro 4-Bay Manual page 44

.The hard drive is fastened to the tray with pins
.The NAS Pro is shipped with screws to mount 2.5-inch hard drives to the hard drive trays
.Remove empty hard drive trays from the NAS Pro .1
.Gently bend the left side of the tray and connect the hard drive to the two pins on the right .2
.Release the left side of the tray and connect the remaining two pins to the hard drive .3
44 4/28/15 Seagate NAS Pro 2-Bay | 4-Bay | 6-Bay