IBM 1 U Installation Manual page 24

10.
Install the tape enclosure in the rack:
a. Extend both slide rails out of the rack cabinet until they lock.
b. Align the rails on the sides of the enclosure with the slide rails in the rack
cabinet; then, slide the enclosure into the rack until it locks into place.
c. Tighten the two thumbscrews on the front of the enclosure to secure the
enclosure to the rack.
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IBM 1 U Rack Mount Tape Enclosure: Installation Guide