IBM RT User's Setup Manual page 208

14. Put whichever drive adapter your system uses back in the
appropriate slot as shown below, and replace the screw.
15. If this is the last drive to be installed, replace the cooling fan
assembly. See "Cooling Fan Replacement" on page 2-6.
16. If there are other options to be installed, do so now, and then
check out the system using Section 9, "Checking Out the
Option Installation" on page 9-1.
Section 2. Removing and Installing Drives in IBM 6150, 2-33